The Cambridge natural history, Vol. 02 (of 10)

by Frank E. Beddard; W. B. Benham; F. W. Gamble; Marcus Hartog; Lilian Sheldon

POLYZOA

BY

SIDNEY F. HARMER, M.A.

Fellow of King's College, Cambridge

CHAPTER XVII

POLYZOA

INTRODUCTION—GENERAL CHARACTERS AND TERMINOLOGY—BROWN BODIES—HISTORY—OUTLINES OF CLASSIFICATION—MARINE POLYZOA—OCCURRENCE—FORMS OF COLONY AND OF ZOOECIA—OVICELLS—AVICULARIA—VIBRACULA—ENTOPROCTA.

The following pages[^[500]] deal with animals whose very existence is hardly known to those who are not professed naturalists. There are but few Polyzoa which have earned the distinction of possessing a popular name, and most of such names as do exist cannot be found outside treatises on Natural History. It is true that many of the members of this group have been vaguely termed "Zoophytes"; but this term implies no more than that they possess a superficial resemblance to certain plants, and it must be remembered that this habit of growth is assumed by many animals which have nothing to do with the Polyzoa. The term "Coralline" is sometimes applied to those calcareous Polyzoa which grow into coral-like forms; and the Tertiary deposit known as the "Coralline Crag" is so called from the large number of fossil Polyzoa which it contains.

The Polyzoa are none the less a most attractive group. Let any one examine a dry piece of a brown paper-like substance (Fig. 232, A), which may be found thrown up on the beach on many parts of our coasts. Of this species (Flustra foliacea), the so-called "sea-mat," an old writer says: "For curiosity and beauty, I have not, among all the plants or vegetables I have yet observed, seen any one comparable to this seaweed."[^[501]] Viewed with the microscope, the frond is seen to consist of two layers, placed back to back, of oblong chambers, each of which is the dried body-wall of a single individual. The whole is obviously a colony, and to this fact the term Polyzoa refers.

The chambers just noticed are termed "zooecia." Each is rounded at one end, near which is the "orifice," through which the tentacles of the living animal can be pushed out. Two short, stiff spines usually occur on each side of the orifice; and the symmetry of this forest of spines fully justifies the above-quoted remark.

Fig. 232.—Flustra foliacea L., Cromer. A, Natural size, B' indicating the portion magnified in B (× 30): a, avicularium with closed mouth, to the left of which are seen two avicularia with open months; o, ovicell, forming the upper part of a zooecium. Ovicells are seen on three consecutive zooecia. The operculum, which closes the orifice of the zooecium, is seen in different positions in the individuals figured.

The upper part of some of the zooecia is somewhat swollen, these swellings representing the conspicuous "ovicells" of many other genera. In the early part of the year each ovicell protects an orange-coloured egg or embryo, and the larvae are readily liberated if the fresh colony be placed in clean sea-water. "At least ten thousand" were hatched out in three hours from a colony placed in a glass by Sir John Dalyell.[^[502]] The larva swims freely in the water for a short time, and should it find a suitable resting-place, it fixes itself and forms the starting-point of a colony, the number of whose individuals is continually increased by the production of buds at the growing edge. The "avicularia" of this species will be alluded to later (see p. [482]).

F. foliacea has long been known to possess in the fresh state a remarkable odour, which is described, according to the fancy of the observer, as a strong odour of fish, or as the smell of violets after a shower. Others have compared it to that of the orange or verbena, or to that of a mixture of roses and geranium.

Flustrella hispida, another of our commonest Polyzoa, which may be found between tide-marks on the stalks of Fucus, consists of a softish brown encrustation, about one-sixteenth of an inch thick, covered by numerous spines. If examined undisturbed in a rock-pool, or transferred to a glass of sea-water, the brown mass will be seen to become surrounded by a delicate bluish halo, which is about as thick as the encrusting mass itself, and consists of the tentacles of the numerous individuals of the colony. The microscope shows that each individual is provided with a circlet of some thirty or more long, delicate tentacles, which together form a graceful funnel (as in Fig. 233). At the bottom of the funnel is the mouth, to which Diatoms or other minute organic particles are conveyed by the cilia which fringe the tentacles. If the tentacles be touched with a needle, the whole funnel is retracted with great rapidity, and in this retracted condition we see no more than the body-walls of the animals. After an interval the tips of the tentacles are cautiously protruded; the tentacles are gradually pushed out, at first in a close bundle, but finally separating from one another to form the funnel which we have already noticed.

There is hardly a more surprising spectacle in the whole animal kingdom than a living fragment of the genus Bugula. The colony grows in the shape of a small tree, whose height may amount to several inches; and is characterised, in many species, by a spiral arrangement of the branches, which makes the genus easy to recognise at first sight (Fig. 233, A). The stem and branches are composed of a single layer of zooecia, arranged two or more abreast. Each zooecium bears, on its outer side, a most singular body termed an avicularium, from its resemblance to a bird's head. Imagine a minute eagle's head attached by a short but flexible neck to the zooecium. Suppose further that this structure moves backwards and forwards in a deliberate but determined fashion, its lower jaw usually widely open so as to be nearly 180° distant from its position when closed. Suppose that the lower jaw is moved by powerful muscles which can be distinctly seen inside the transparent head of the avicularium, and that every now and then it closes with a snap, seizing any unfortunate worm which may happen to be within reach with a grasp of iron. The above gives a very faint idea of the appearance of a living Bugula colony, with its hundreds of swaying avicularia, and with its tentacular funnels protruding from their zooecia, and withdrawing themselves capriciously from time to time.

Fig. 233.—Bugula turbinata Alder, Plymouth. A, A small colony (natural size); B, portion of a branch (× 50): a, a', avicularia, in different positions; ap, "aperture" (see p. [524]); b, polypide-bud, attached by its stomach to b.b, brown body; m, mouth, surrounded by the circle of tentacles; two individuals to the right show the tentacles partially expanded; o, ovicell; s, marginal spine. The avicularia of some of the zooecia have been omitted in B.

General Characters.—The Polyzoa are colonies, leaf-like or tree-like in form, and often strongly resembling seaweeds, or forming encrustations on the surface of stones and water-plants, or taking on other shapes. The units of the colony are complete individuals (Fig. 234). The zooecium or body-wall encloses a body-cavity, in which lies a digestive canal, with which are closely connected the central nervous system and the retractile, ciliated tentacles. The structures other than the zooecium constitute the "polypide." The mouth (m) leads into the ciliated pharynx (ph) which is followed by the oesophagus (oe) which again passes into the stomach (s), whose walls are coloured by a characteristic yellowish pigment. The stomach gives off the intestine (in), which is lined by strong cilia, by means of which a rotatory movement is given to the faeces contained in it. This communicates by a narrow passage with the rectum (r), which opens by means of the anus (a).

Fig. 234.—Alcyonidium albidum Alder, Banyuls-sur-Mer. Diagram showing the structure of a single zooecium with its polypide retracted: a, anus; d, diaphragm; e, ectocyst; em, ectoderm; f, funiculus; g, ganglion; i, intertentacular organ; in, intestine; m, mouth; mm, mesoderm of body-wall; o, orifice; oe, oesophagus; ov, ovary; p, parietal muscles; ph, pharynx; p.v, parieto-vaginal muscles; r, rectum; r.m, retractor muscles (contracted); s, stomach; t, testis; tn, tentacles; t.s, tentacle-sheath or kamptoderm. (After Prouho.[^[503]])

In the retracted condition the tentacles (tn) lie in a cavity which opens to the exterior by the orifice (o). The cavity is bounded by a thin membrane termed the "tentacle-sheath" (ts), and it is incompletely subdivided, near its upper end, by a diaphragm (d), perforated by a circular hole through which the tentacles can be protruded. The diaphragm bears the thin folded collar characteristic of the Ctenostomata, the group to which the species figured belongs (see p. [477]).

Fig. 238, B, shows the tentacles of Bowerbankia in their fully expanded and partially expanded condition. Comparing this with Fig. 234, it will be clear that when protrusion is taking place, the tentacles are forced in a bundle, tips first, through the diaphragm and next through the orifice of the zooecium, the alimentary canal offering no resistance to this movement, owing to the length of the oesophagus. A moment's consideration will show that the bases of the tentacles, in passing through the orifice, will carry with them that part of the flexible tentacle-sheath to which they are attached; and it will further be clear that so much of the tentacle-sheath as is thus protruded will be turned inside out. This process of "evagination" continues until its further progress is stopped by the retractor-muscles (r.m), and by the parieto-vaginal muscles (p.v), which pass from the interior of the body-wall to the upper part of the tentacle-sheath. The latter has now become the delicate layer which connects the expanded tentacles with the zooecium; and the anus (Fig. 238, C, a) opens directly to the exterior. Since the name "tentacle-sheath" is thus descriptive of the condition of retraction only, the term "kamptoderm"[^[504]] has been suggested as an alternative name.

The presence of a complete digestive canal and the ciliation of the tentacles in Polyzoa are conspicuous differences between these animals and the Hydroids, with some of which the Polyzoa may have a marked external similarity.

The outermost[^[505]] layer of the body-wall is known as the "ectocyst" (Fig. 234, e). This may be densely calcareous, in which case the dried Polyzoon differs little in appearance from the living animal with its tentacles retracted; or it may be partially calcified, or it may consist entirely of a flexible cuticle, as in Fig. 234. The ectocyst is prolonged through the orifice (o) as far as the diaphragm (d).

Forms with a calcareous ectocyst are commonly ornamented with ridges or other patterns, which are often of great beauty. The ectocyst in these cases is commonly interrupted at intervals by pores (Fig. 239, C), into which processes of the "endocyst"—the living, internal part of the body-wall—extend. These may appear as superficial pores, which apparently open to the exterior in the dried condition, or they may perforate the septa between adjacent individuals. This may be strikingly demonstrated by decalcifying a branch of Crisia (Fig. 237), in which the zooecia then appear connected by numerous strands of tissue. In many marine forms the communications between the individuals are in the form of small sieve-like plates known as "rosette-plates."

The endocyst may consist of definite layers of ectoderm (em) and mesoderm (mm), as in Fig. 234, but the mesoderm is commonly in the form of a loose network, some of which is attached to the body-wall, some to the alimentary canal, some forming connecting strands between these two layers, and other cells floating about freely in the body-cavity. These mesodermic structures are often spoken of as the "funicular tissue," since one or more strands of it commonly take on the form of a definite "funiculus" (f). This structure may bear the ovary (ov), while the testes (t) are found, commonly in the same zooecium, attached to various parts of the body-wall. The eggs and spermatozoa, when ripe, break off and float freely in the body-cavity.

The funicular tissue was at one time described as a "colonial nervous system." The idea expressed by this term must be considered erroneous from the fact that no nervous co-ordination of the individuals is known to exist, in the vast majority of cases. The actual nervous system consists of a ganglion (g) placed between the mouth and anus of each polypide, and lying in a small circular canal (not shown in Fig. 234) which immediately surrounds the oesophagus. This canal is developed in the bud as a part of the body-cavity, from which it becomes completely separated in marine forms. The Polyzoa have no vascular system.

Brown Bodies.—In the majority of cases, an extraordinary process of regeneration takes place periodically during the life of each zooecium. The tentacles, alimentary canal, and nervous system break down, and the tentacles cease to be capable of being protruded (Fig. 235, 1). The degenerating organs become compacted into a rounded mass (Fig. 235, 2 and 3, b.b), known from its colour as the "brown body." This structure may readily be seen in a large proportion of the zooecia of transparent species. In active parts of the colony the body-wall next develops an internal bud-like structure (Fig. 235, 1, b), which rapidly acquires the form of a new polypide (Fig. 235, 2 and 3). This takes the place originally occupied by the old polypide, while the latter may either remain in the zooecium in the permanent form of a "brown body," or pass to the exterior. In Flustra the young polypide-bud becomes connected with the "brown body" by a funiculus (Fig. 235, 1, 2). The apex of the blind pouch or "caecum" of the young stomach is guided by this strand to the "brown body," which it partially surrounds (3). The "brown body" then breaks up, and its fragments pass into the cavity of the stomach, from which they reach the exterior by means of the anus.

Fig. 235.—Flustra papyrea Pall. Naples. × 50. Illustrating the development of a new polypide after the formation of a "brown body." In 1, a, two masses formed from the alimentary canal; b, young polypide-bud; b.b, degenerating tentacles; c, connective tissue: 2, another zooecium, later stage; b.b, brown body; r.m, retractor muscles; s, stomach; t, tentacles of new polypide; t.s, tentacle-sheath: 3, the same zooecium, 191 hours later; letters as in 2. 1 and 2 are seen from the front, 3 from the back.[^[506]]

There is some reason to believe[^[507]] that these remarkable processes are connected with the removal of waste nitrogenous matters. The Marine Polyzoa are not known to be, in most cases, provided with definite excretory organs, although it is possible that the intertentacular organ (Fig. 234, i) described on p. [508] may in some cases perform excretory functions. There can, however, be little doubt that some kind of excretion takes place in the Polyzoa; and in considering what organs could possibly perform this work, our attention is arrested by the alimentary canal. The digestive organs of the young bud are perfectly colourless. As growth proceeds, certain parts acquire a yellowish, and later a brown colour. The degeneration of the polypide is followed by the grouping of large numbers of the free cells of the body-cavity into a mass which closely surrounds the incipient "brown body." Under their action, the latter becomes considerably smaller, probably as the result of the absorption of matters of nutritive value into other tissues. The final result is the formation of the compact "brown body," whose colour is principally derived from the pigment formerly present in the alimentary canal. Experiments made by introducing into the tissues of the Polyzoa certain artificial pigments which are known to be excreted by the kidneys when injected into the bodies of other animals, have given some reason for believing that the appearance of the brown pigment in the wall of the digestive organs is, in part, a normal process of excretion; although that process is not entirely carried out by the organs in question.

Little is known with regard to the duration of life of a single polypide; but some information bearing on this question may be obtained from a set of observations made on Flustra papyrea.[^[508]] The table gives the number of days from the time at which the polypides were noticed to commence their degeneration:—

Days.
2	"Brown body" partially formed, the parts of the polypide being still easily recognisable.
5	Tentacles still just recognisable: appearance of new polypide-bud.
8	Stage shown in Fig. 235, 2.
11	Union of apex of stomach with "brown body."
16	"Brown body" half surrounded by stomach, and preparing to break up (Fig. 235, 3).
21	"Brown body" broken up into numerous fragments, contained in the alimentary canal of the new polypide.
35	"Brown body" almost completely absorbed.[[509]]

These results did not hold good for all the zooecia in a single colony. In some, the "brown body" was not completely got rid of at the end of sixty-eight days, the conclusion of the experiment.

So striking are the facts relating to the "brown bodies" that it has been believed[^[510]] that what we have above described as the individual really consists of two kinds of individuals: firstly, the "polypide" or complex of tentacles and digestive organs; and secondly, the "zooecium," or house of the zooid or polypide, corresponding with what has been described above as the body-wall. The one individual, the zooecium, is on this view provided with successive generations of the second kind of individual, the polypide; and these latter function as the digestive organs of the two-fold organism. This view, though fascinating at first sight, is not borne out by an examination of all the facts of the case, especially when the Entoprocta are taken into account.

History.—The history of the Polyzoa, as far as 1856, has been fully treated by Allman in his great work on the Fresh-water Polyzoa;[^[511]] but a few words may be said on this subject.

The Polyzoa attracted comparatively little attention before the beginning of the present century. Originally passed over as seaweeds, their real nature was established in connexion with the discovery of the animal nature of corals. So great a revolution could hardly be accepted without a struggle, and even Linnaeus went no further in this direction than to place them in a kind of half-way group of "zoophytes," whose nature was partly animal and partly vegetable. It is hardly necessary to point out that this view has now been abandoned by common consent; and indeed there is no more reason for regarding an animal as showing an approach to the plants because it grows in the external semblance of a seaweed than there would be for supposing a bee-orchid to be allied to the animal kingdom because of the form of its flowers.

But the claims of the Polyzoa to rank as a separate class were by no means admitted with the discovery that they were animals. They were still confounded with Hydroids, Alcyonarians, or Corals until their possession of a complete alimentary canal was recognised as a feature distinguishing them from those animals. This was principally due to the observations of J. V. Thompson[^[512]] in Ireland, who introduced the term Polyzoa; and of C. G. Ehrenberg[^[513]] in Germany, who proposed the class-name Bryozoa, or moss-like animals.

It is impossible to avoid all mention of the controversy which has raged with regard to these two rival terms. The controversy is for the present at rest, the name Polyzoa being employed by the majority of English writers, amongst whom must be mentioned Allman, Busk, Hincks, and Norman, admittedly authorities of the first rank; while Bryozoa is employed by practically all the Continental writers.

The priority of Thompson's name is unquestioned. While Ehrenberg, however, definitely introduced Bryozoa as the name of a group, Thompson was less precise in this respect, although he states[^[514]] that his discovery "must be the cause of extensive alterations and dismemberments in the class with which they [the Polyzoa] have hitherto been associated." Thompson, in fact, clearly understood that the Polyzoa could no longer rank with the Hydroids. The controversy has been summarised by Hincks, in his History of the British Marine Polyzoa,[^[515]] where references to other papers on the same subject are given.

The Polyzoa were associated by H. Milne-Edwards with the Tunicata in the group Molluscoidea (Molluscoïdes[^[516]]), to which the Brachiopoda were afterwards added by Huxley.[^[517]] A knowledge of the development of the Tunicata has, however, shown that these animals must be withdrawn from any association with the other two groups; while there is little real evidence that even the Brachiopods have anything to do with the Polyzoa.

Classification.—The Polyzoa are divided into two sub-classes:—I, the Entoprocta; and II, the Ectoprocta.[^[518]] Although the character referred to by these terms is merely the position of the anus with relation to the tentacles,[^[519]] there can be no doubt that the two groups differ widely from one another in many important respects. I do not, however, accept the view, maintained by some authors, that the Entoprocta and the Ectoprocta are two separate classes which are not nearly related.

The base from which the whole set of tentacles springs is known as the "lophophore."[^[520]] In the Entoprocta (Fig. 236, 1) the lophophore is circular; the mouth is situated near the margin of the area surrounded by the tentacles; and the anus is found within the circlet, near the end opposite to the mouth.

In (2) and (3), representing the Ectoprocta, the anus is outside the series of tentacles. In the majority of cases, including all the marine Ectoprocta and one or two of the fresh-water forms, the lophophore is circular (2), the mouth occurring at the centre of the circle, and not being provided with a lip. These forms of Ectoprocta constitute the Order Gymnolaemata,[^[521]] the dominant group of the Polyzoa in respect of number of genera and species. The remaining Ectoprocta belong to the exclusively fresh-water Order Phylactolaemata,[^[522]] in which the mouth is protected by an overhanging lip or "epistome"; the ground-plan of the tentacles is, except in Fredericella, horse-shoe shaped (Fig. 236, 3), and the tentacles themselves are usually much more numerous than in the other cases.

Fig. 236.—Ground-plan of the lophophore in (1) Entoprocta, (2) Gymnolaemata, (3) Phylactolaemata: a, anus; ep, epistome; m, mouth. The tentacles are represented by shaded circles.

The general characters of these divisions will be more easily understood by referring to the figures given of living representatives of the groups. The Entoprocta are illustrated by Figs. 243-245; the Gymnolaemata by Figs. 238, 240; and the Phylactolaemata by Figs. 247, 248.

The Gymnolaemata include three Sub-Orders:—

1. Cyclostomata.[^[523]]—Body-wall densely calcareous, the zooecia being more or less tubular, usually with a circular orifice (Fig. 237).

2. Cheilostomata.[^[524]]—Body-wall of varying consistency. The orifice is closed, in the retracted state of the polypide, by a chitinous lip or "operculum," which is more or less semicircular (Figs. 239, 241).

3. Ctenostomata.[^[525]]—Body-wall always soft. The cavity into which the tentacles are retracted is closed by a frill-like membrane, the edges of whose folds have some resemblance to the teeth of a comb. This membrane, the "collar," is seen in different conditions of protrusion or retraction in Figs. 234, 238. The stomach may, in this group, be preceded by a muscular gizzard (Fig. 238, C, g).

Occurrence.—By far the larger number of the Polyzoa are inhabitants of the sea. A recently published catalogue[^[526]] of marine Polyzoa includes nearly 1700 living species; and of these, the great majority belong to the Gymnolaemata. This group is further known to include an enormous number of fossil forms. Not only do we find that in living Polyzoa the members of a single Order largely outnumber the remainder of the Polyzoa, but we may further notice that the Cheilostomata, one of the sub-Orders of the dominant group, are at present largely in excess of the whole of the rest of the Polyzoa taken together.

Polyzoa may be collected with ease on almost any part of our coasts. The fronds of the "sea-mat" (Flustra foliacea) are thrown up by the waves in thousands in places where the bottom is shallow and sandy. The bases of the larger seaweeds growing on rocks between tide-marks are nearly always thickly covered with encrustations of Flustrella hispida or of species of Alcyonidium, in places where they are kept moist by being covered with a sufficiently thick layer of other algae. Rocks which are protected from the sun may be coated with calcareous Cheilostomes; and these are also found, in company with branching Polyzoa of various kinds, on the bases of the Laminaria thrown up by gales or exposed at spring tides. The graceful spirals of Bugula turbinata (Fig. 233, A) may be found hanging from the rocks at extreme low water; while colonies of Scrupocellaria, remarkable for their vibracula (see p. [484]), are common in many places between tide-marks. Certain species affect the mouths of estuaries.

Membranipora membranacea commonly covers many square inches of the frond of Laminaria with its delicate lace-like encrustation. Nitsche[^[527]] has shown that this species has its calcareous matter deposited in plates, separated by intervals of uncalcified ectocyst. The effect of this arrangement is to make the colony flexible, and to enable it to adapt its shape to the movements of the Laminaria, which is swayed to and fro by the action of the waves. Many of the calcareous forms growing on Laminaria have no special arrangement of this kind, and they accordingly grow in colonies whose area is so small that the greatest movements to which the seaweed is liable are not sufficient to crack or break the colony.

Many species show a decided, or even exclusive, preference for particular situations; as, for instance, species of Triticella, which are only found on certain Crustacea. Many encrusting forms prefer the inside of dead shells of Pecten, Cyprina, etc., to any other habitat. Terebripora[^[528]] excavates tubular cavities in the substance of the shells of Molluscs. Hypophorella[^[529]] inhabits passages which it forms in the walls of the tubes of the Polychaets, Lanice and Chaetopterus. Lepralia foliacea, one of the Cheilostomata, forms masses which may reach a circumference of several feet, simulating a small coral-reef. Its contorted plates are a regular museum of Polyzoa, so numerous are the species which delight to find shelter in the quiet interstices of the colony. The exquisite little colonies of Crisia eburnea are commonly found on red seaweeds, or on the branches of the Hydroid Sertularia.

The Polyzoa are found at all depths, certain Cheilostomes having been recorded from 3000 fathoms. The Cyclostomes dredged by the "Challenger" were all found in depths of 1600 fathoms or less, while the Ctenostomes are a distinctly shallow water group, most having been found at less than 40 fathoms, and only three at so great a depth as 150 fathoms.[^[530]]

A few forms (Membranipora pilosa, Scrupocellaria reptans, etc.) are known to be phosphorescent;[^[531]] but it is not known what is the purpose of this phenomenon.

External Form.—The Polyzoa may be roughly divided into (1) encrusting forms, usually calcareous, but sometimes soft; and (2) erect forms, which are either rigid or flexible. This flexibility can coexist with a highly calcified ectocyst, as in Crisia (Fig. 237), Cellaria, and others in which the branches are interrupted at intervals by chitinous joints. The coral-like forms may assume the most exquisite shapes, pre-eminent among which are the lovely net-like colonies of Retepora. Polyzoa of this type are seldom found between tide-marks, where their brittle branches would be liable to be snapped off by the waves. The erect species which occur in such positions are flexible, although flexible species are by no means restricted to the zone between tide-marks.

Fig. 237.—Crisia ramosa Harmer, Plymouth. A, End of a branch, × 1; B, another branch, × 20, showing the chitinous joints, the tubular zooecia characteristic of Cyclostomata, and the pear-shaped ovicell with a funnel-shaped orifice at its upper end.

Although the form of the colony is very different in different Polyzoa, a pocket-lens will usually show whether a given specimen belongs to the group or not. The surface is nearly always more or less distinctly composed of zooecia, or at least shows their orifices. The entire colony may be built up of these zooecia; and this is by far the commonest arrangement, both in encrusting and in erect forms. In certain genera, however, and particularly in some Ctenostomes (Fig. 238), and in most of the Entoprocta, the individuals grow out at intervals from a cylindrical stem or "stolon" (st), which is not composed of zooecia.

The Cyclostomata may assume an erect or encrusting habit. Their zooecia are always more or less cylindrical; the upper ends being often completely free, although in many cases the whole zooecium is closely adnate to its neighbours. In the breeding season the forms which belong to this group are provided with curious "ovicells," which contain the embryos. These may either be pear-shaped swellings on the branches (Crisia, Fig. 237), or they may form inflations of the surface, between the zooecia. The mature ovicell is provided with one or more openings, through which the larvae escape.

Fig. 238.—Bowerbankia pustulosa Ell. and Sol., Plymouth. A, Fragment of a colony, natural size, showing the branching stem, bearing tufts of zooecia: B, one of these tufts, with the growing apex of the stem (st), × 27; b, young zooecia (buds); c, the "collar" characteristic of Ctenostomata; t, tentacles; C, a single zooecium, with expanded tentacles, more highly magnified; a, anus; c, collar; g, gizzard; i, intestine; o, oesophagus; s, stomach.

The Ctenostomata rarely have even the slightest trace of calcareous matter. Alcyonidium and its allies form soft encrustations, or may even grow into erect masses six inches or more in height (A. gelatinosum). In this type the zooecia are often so closely united that it may be difficult or impossible to make out their limits in the living colony. Many of the dendritic or branching Ctenostomes (Fig. 238) are characterised by an extreme delicacy of habit. The zooecia in these cases are sharply marked off from the stem. They are either cylindrical or ovoid, being commonly attached by a very narrow base, so that in some species they readily fall off, and may thus be completely absent in certain parts of the colony. In such forms as Vesicularia spinosa, it requires considerable experience to recognise a stem which has lost its zooecia as being part of a Polyzoon. In Mimosella the zooecia possess a remarkable power of movement on the stem, similar to that possessed by the leaflets of the Sensitive Plant.[^[532]] In certain forms (Bowerbankia, Amathia) the zooecia occur in groups separated by intervals which are devoid of zooecia, but in other cases they may have a more irregular arrangement. The collar to which this group owes its name is by no means a conspicuous feature. Its position when retracted has been shown in Fig. 234, while Fig. 238 further illustrates its relations.

The Cheilostomata grow in a great variety of forms, and also show a wide range of character in their zooecia. The orifice is commonly surrounded by stiff spines (Fig. 257, p. [524]), which perhaps have the function of protecting the delicate polypides from the sudden impact of foreign bodies. These spines may attain an enormous development, as in Bicellaria ciliata, and some forms of Electra (Membranipora) pilosa (Fig. 256, A).

The operculum is usually, though by no means always, a conspicuous feature of the Cheilostome zooecium. It is invariably of chitinous consistency, and is more or less semicircular in outline, the straight edge forming a hinge on which the operculum opens. In some cases the orifice is surrounded by a raised margin or "peristome" (Fig. 255, B, C); the operculum is then situated at the bottom of a depression of the surface, and may be concealed from view. In others, in which the front wall of the zooecium is membranous (Bugula, Fig. 233), the operculum is merely a part of this membrane, and so is quite inconspicuous; and in cases of this kind the membranous wall may be protected by an arched spine, the "fornix," developed from one side of the zooecium (Fig. 254, f). The ovicells are commonly a conspicuous feature of this group, although they are believed to differ fundamentally from those of Cyclostomata. They have the form of a helmet-like covering overhanging the orifice (Figs. 240, 241), and may be either prominent or more or less concealed by the growth of adjacent parts of the zooecia. The presence of ovicells of this description is perfectly distinctive of the Cheilostomata.

Avicularia and Vibracula.—Most singular of the external appendages of the Cheilostomata are the extraordinary "avicularia" and "vibracula" of some genera.[^[533]] By the comparison of a carefully selected series of genera, it has been established that the avicularium is a special modification of a zooecium. One of its least modified forms is found in Flustra foliacea (Fig. 232), where the avicularia (a) are small zooecia with a conspicuously large operculum ("mandible"). Avicularia of a similar type occur in Cellaria (Fig. 239, A), Schizotheca, etc., the avicularium occupying the place of an ordinary zooecium. These are the "vicarious" avicularia of Mr. Busk.[^[534]]

Fig. 239.—Forms of avicularia. A, Cellaria fistulosa L., Plymouth, × 43; a.z, avicularian zooecium, with closed mandible; o, operculum of zooecium: B, Schizoporella unicornis Johnst., Scilly Is., × 43; zooecium bearing two avicularia; m, opened mandible of avicularium; s, sinus of orifice: C, zooecium of Smittia landsborovii Johnst., Plymouth, × 43; the operculum is seen at the bottom of a depression surrounded by a thin collar or "peristome," in an emargination of which is seen an avicularian zooecium (a.z); m, mandible (opened); p, pores; t, tooth.

In the next stage (Figs. 239, B, 256, B) the avicularian zooecium is further reduced; it has in most cases lost its place in the series of individuals, and is found instead seated on some part of an ordinary zooecium ("adventitious" avicularia). The avicularium now consists of a much reduced zooecium, bearing the well-developed operculum or mandible.

Having arrived at this point, the avicularia seem to lose all sense of the propriety of remaining in the positions once occupied by zooecia. They have become degraded to the rank of appendages of the zooecia, and as such they may occur in an astonishing variety of positions. Sometimes one occurs on each zooecium in the middle line, or asymmetrically, or even on the top of the ovicell; in other cases the orifice is flanked by an avicularium on each side (Fig. 239, B). Sometimes (Cellepora) the avicularia are of more than one kind, some being large and some small, some having a pointed mandible and others a mandible with a rounded spoon-like end.

In the cases so far considered, the body of the avicularium is fixed. The highest differentiation acquired by these structures occurs in cases like Bugula, where they are borne on flexible stalks, which may even exceed the avicularia in length.[^[535]]

Fig. 240.—Bugula turbinata, showing avicularia (a, a'). The figure is explained on p. [468].

In Bugula turbinata (Fig. 240) each zooecium is provided with one of these appendages, attached to the base of the outer of the two spines which border its orifice. The avicularia of the two edges of the flattened branch are much larger than those of the more internal zooecia. The upper jaw is strengthened by a kind of buttress, or thickening of the ectocyst, which passes on each side across the avicularium to the hinge-line of its mandible. The upper part of the beak is strongly hooked, while the tip of the mandible bears a prominent spike, which fits inside the upper beak when the jaw snaps. A great part of the head is filled with a strong muscle, whose fibres exhibit a distinct transverse striation, and converge into a median tendon. The latter is inserted into the middle of the mandible. The muscle serves to close the jaws, and is the representative of the muscles by which the operculum is closed in an ordinary zooecium. The lower jaw is opened by means of a pair of muscles which are situated immediately under the ectocyst of the avicularium, and pass into the mandible close to its hinge.

Fig. 241.—Illustrating the transition from avicularia to vibracula. A, Microporella ciliata Pall., Scilly Is., × 62; a, avicularium with short mandible (closed); a', avicularium with vibraculoid mandible (open); m.p, median pore; o, ovicell: B, Mastigophora dutertrei Aud., Shetland Is., × 47; s, sinus of orifice; v, seta of vibraculum (or vibraculoid avicularium).

Within the jaws, in the region which we may term the palate, is a rounded knob, which bears a tuft of delicate sensory hairs, which doubtless enable the avicularium to recognise the presence of any foreign body. The closure of the mouth may, indeed, be instantaneously induced by touching it with the point of a needle. It has been suggested that a small mass of cells which bears these hairs may represent the rudiment of the polypide.

The "vibraculum" (Fig. 242) is regarded as an avicularium in which the mandible has become elongated, so as to form a thin, chitinous "seta," which from time to time moves through the water. The part of the vibraculum which represents the zooecium commonly bears a tubular rootlet, used for attaching the colony to the substance on which it is growing (Fig. 254, p. [517]).

In Microporella ciliata (Fig. 241, A) the avicularia are very variable, and in some cases take on a "vibraculoid" character. But in the fully-developed vibraculum (Fig. 242) there is usually no such compromise of characters. It may, however, be noted that Scrupocellaria scabra (Fig. 254), which belongs to a genus characterised by its highly differentiated vibracula, possesses structures (v.z) which could hardly be distinguished from avicularia were it not for the presence of the rootlet (r).

In the course of some observations which I had the opportunity of making on Bugula calathus at Naples, a fine hair offered to a small colony was seized with such force by the avicularia that the entire colony was lifted out of the water by the hair. The same colony had captured (1) a small Nereis, which it held with several of its avicularia; (2) an Anisopod Crustacean, 2½ mm. long; and (3) a small Amphipod, which was held by one of its antennae. The Anisopod was held by the tip of one leg with one avicularium, and by the penultimate joint of one of its chelae with an avicularium of another branch. It was captured in such a way that its chela, the "hand" of which was about half as long as the avicularium, actually closed on to the avicularium without being able to effect its escape. A little later the other chela was caught by another avicularium. Curiously enough, however, an avicularium did not necessarily close even when part of a captured animal was actually in its mouth. The avicularia made no attempt to place themselves in an advantageous position for catching fresh parts of the Nereis, which they might easily have done. The avicularia which had captured prey remained motionless. The others moved backwards and forwards (cf. the various positions of the avicularia shown in Fig. 240) ten times in ¾ to 1 minute, snapping their jaws perhaps once in that time. The two Crustacea were still retained by the avicularia two days later. On the next day they had both disappeared; but the colony had again caught the Nereis, which had previously effected its escape with the loss of nearly all its tentacular cirri.

These observations, and others which have been recorded, do not, unfortunately, give any information as to the purpose of the movements of the avicularia and vibracula. It is obvious that they may be defensive in character; and it cannot be doubted that the avicularia can prevent inquisitive worms from straying at will over the surface of the colony. There is no evidence to show that animals are discouraged from interfering with a Bugula owing to the presence of its defensive weapons.

Fig. 242.—Caberea ellisii Flem., Norway. × 40. Back view of part of a branch. The large vibracular zooecia (v.z) occupy nearly the whole of the surface. s, Seta of vibraculum; z, zooecia.

It is not, indeed, certain what are the enemies against which the Polyzoa have specially to guard. Sea-urchins and certain Molluscs are known to browse on Polyzoa. Fresh-water Polyzoa, in which avicularia and vibracula are absent, are attacked by the larvae of Insects, and by Triclad Planarians. I have found the latter with their long pharynx everted and completely buried in a Cristatella colony. It is possible that some marine Cheilostomes may be saved from attacks of this kind owing to the existence of their armoury of avicularia and vibracula. It is also possible that these structures are of service by removing foreign particles which might otherwise settle on the colony, and tend to block up its orifices. It has further been suggested that animals seized by the avicularia may be held until they die, and that their disintegrating particles may then be carried to the mouths of the polypides by the ciliary currents of the tentacles; but proofs of this suggestion are wanting, and it must be admitted that the subject needs further elucidation.

The vibracula ordinarily remain stationary for some little time, every now and then giving a sweep through the water. In the majority of cases these structures, like the avicularia, act perfectly independently of one another, so far as can be made out; but in Caberea (Fig. 242) the vibracula move in unison, the simultaneous action of the whole series, after a period of quiet, being described as "positively startling."[^[536]]

It has been stated by Busk[^[537]] that the entire colony in Selenaria and Lunulites may be moved from place to place by the large vibracula which these forms possess.

Fig. 243.—Pedicellina cernua Pall., Guernsey. Entire colony. × 27. The colony has three growing ends, a; 1-8, individuals of colony; 1 and 8 are quite immature; and 7 (tentacles retracted) is still young; 2, is seen in longitudinal section; g, generative organ, and below it the ganglion; m, mouth; r, rectum; s, stomach; between g and r are three embryos in the brood-pouch; the tentacles are retracted; in 5 and 6 the tentacles are expanded; in 6 two embryos are seen within the circle of the tentacles, to the left of them is the rectum, and to the right the mouth; 3 is in the act of losing its calyx, and has already developed the beginning of a new polypide-bud; in 4 the primary calyx has been lost, and the new calyx is clearly marked off from the stalk.

Entoprocta.—The Entoprocta, although a very small sub-class, deserve special consideration, if for no other reason, from the fact that many writers regard them as the most primitive group of Polyzoa, and consequently as the forms which show most affinity to other classes of animals.

Their most obvious characteristic is, as we have already seen,[^[538]] the position of the anus within the circle of tentacles. The individuals formed by budding always remain more separate from one another than those of most Ectoprocta.

The commonest Entoproctous genus is Pedicellina, a graceful little animal, which occurs on many parts of our coast. It may often be discovered by looking carefully on the pink, jointed, calcareous alga, Corallina, which may be found growing at the edges of deep and cool rock-pools not too far above low-water mark. Its creeping stem or "stolon" is firmly attached to the surface of the seaweed, and sends off vertical stems here and there.[^[539]] Each stem bears a "calyx," which is practically an individual of the colony. The stolon terminates, at one or both ends, in a growing-point (a), from which new individuals are budded off. The stalks bend from time to time in a curious spasmodic manner, by which means the calyces are moved about with an irritable and angry air. A good idea of the way in which the tentacles are folded away when the animal is disturbed may be obtained by putting the two wrists together, with the fingers spread out to represent the tentacles, the retraction of which would be represented by turning the tips of the fingers down into the space, the "vestibule," between the two palms. A delicate fold of skin growing from the edge of the calyx closes over the retracted tentacles, owing to the contraction of a sphincter muscle present in its circular edge. The body-wall is not separated from the alimentary canal by a definite body-cavity, so that there is no obvious distinction between the polypide and the zooecium. The existence of the Entoprocta is in fact a strong reason for refusing to admit that these two terms correspond with two different kinds of individuals.

Let us now imagine the condition we should have if a large and continuous cavity were developed between the alimentary canal and the body-wall. The body-wall would clearly have the general relations of a zooecium, while the alimentary canal and tentacles would obviously correspond with the polypide. The existence of the body-cavity would make it possible for the animal to retract its tentacles instead of merely turning them in. Regarded in this way, there is but little difficulty in comparing the Ectoprocta with the Entoprocta.

The calyces are deciduous, i.e. they are lost from time to time, the end of the stalk then producing a polypide-bud, which forms the vestibule and alimentary canal of a new calyx. Hence the phenomenon which may so commonly be noticed in Pedicellina of a "young head on old shoulders." The loss of the calyces may have some relation to the formation of the "brown bodies" in the Ectoprocta.

Another Entoproct, Loxosoma (Fig. 245) is remarkable for being the only Polyzoon which is not colonial. The buds, which are formed in two lateral series, break off as soon as they are mature, and at once begin to lead an independent existence. Loxosoma is further remarkable for being almost invariably found commensally with other animals, where it may occur in enormous numbers. L. phascolosomatum, common in the Channel Islands, is only found on the tip of the tail of Phascolosoma (see p. [428]), which inhabits the mud of Zostera-beds. Other species are found on the external surface of certain sponges (Tethya, Euspongia, Cacospongia); or on the outside of a compound Ascidian, Leptoclinum, which may itself be carried about as a detachable covering on the back of a crab (Dromia). Another species is found on the ventral surface of the Polychaet Aphrodite, and of its ally Hermione.

Fig. 244.—Side view of Loxosoma annelidicola Van Ben. and Hesse. × 50. (From Prouho.)

L. annelidicola, an interesting species recently investigated by Prouho,[^[540]] was originally described in 1863 as a Trematode, under the name of Cyclatella. It escaped further notice until it was again found in the neighbourhood of Roscoff, in Brittany, on certain Polychaets belonging to the family Maldanidae (see p. [332]). The calyx has a very flattened form, and is borne on a short stalk, which terminates in a large attaching disc, formerly mistaken for the sucker of a Trematode. The features in which this species differs from other members of the genus are shown by M. Prouho to be correlated with its mode of life. The animal has the habit of lying flat on its back, the disc at the end of its stalk being firmly attached to the skin of the worm, and its short stalk being bent round into a curve so as to bring the calyx into a supine position, with its lophophore directed upwards. This habit, together with its flattened form, prevents it from being crushed between the worm and its tube. But without some further provision its position might be merely a source of danger. For supposing the calyx to be directed backwards in relation to the worm, a sudden backward movement of the latter into its tube might bring the Loxosoma into fatal contact with the inner surface of the tube. There would obviously not be sufficient room to turn round in a vertical plane, so as to bring the body into a position of safety, i.e. into a position in which it moves stalk first. But by a beautiful arrangement of the muscles of its stalk this movement is effected in a horizontal plane; on touching the Loxosoma with the point of a needle it would swing round in this way through 180° with "une rapidité qui étonne."

Urnatella[^[541]] is a beautiful form with a segmented stalk, the stalks usually arising in pairs from a common base. It has at present only been found in fresh water in the United States.

Fig. 245.—Diagram of the structure of Loxosoma, seen from the oesophageal side. × about 70. a, Anus; b, buds; e, excretory organ; f, foot-gland; g, ganglion; gn, generative organs; o, orifice of vestibule; oe, oesophagus; s, stomach; t, retracted tentacles.

In Pedicellina the plane of the lophophore is at right angles to the stalk, which is separated from its calyx by a marked constriction. In Loxosoma the lophophore is set obliquely,[^[542]] and there is no constriction at the base of the calyx. In Urnatella we find an intermediate condition, the lophophore resembling that of Loxosoma, while the constriction at the base of the calyx is similar to that of Pedicellina. Since the latter is known to pass in its development[^[543]] through a stage with an oblique lophophore, it may be presumed that Loxosoma is a more archaic form than Pedicellina. In other respects, the structure of the Entoprocta is very constant, whatever the genus.

A pair of ciliated excretory tubes open into the vestibule. These are similar in structure to the "head-kidneys" of the larvae of Polychaet worms, or to the excretory organs of adult Rotifers. Flame-cells have been described by Davenport in the stalk of Urnatella, but it is not known whether they are connected with the excretory tubes of the calyx. The animals are either hermaphrodite or have separate sexes, and the generative organs open by ducts of their own into the vestibule. The nervous system consists of a ganglion placed between the mouth and the anus, giving off a set of nerves, many of which end in delicate tactile hairs placed on the tentacles or other parts of the body.[^[544]]

CHAPTER XVIII

POLYZOA (continued)

FRESH-WATER POLYZOA—PHYLACTOLAEMATA—OCCURRENCE—STRUCTURE OF CRISTATELLA—DIVISION OF COLONY—MOVEMENTS OF COLONY—RETRACTION AND PROTRUSION OF POLYPIDES IN POLYZOA—STATOBLASTS—TABLE FOR DETERMINATION OF GENERA OF FRESH-WATER POLYZOA—REPRODUCTIVE PROCESSES OF POLYZOA—DEVELOPMENT—AFFINITIES—METAMORPHOSIS—BUDDING.

Fresh-water Polyzoa.—Although the Gymnolaemata are ordinarily marine animals, fresh-water examples from this Order are not altogether wanting. The Ctenostomata among the typically marine groups show the most tendency to stray into fresh-water.

Alcyonidium and Bowerbankia (Fig. 238) flourish in estuaries, while Victorella and Paludicella (Fig. 250) are only known as fresh or brackish water forms. Victorella was named after the Victoria Docks in London, where it was first found; more recently it has also been discovered in other parts of England and on the Continent.[^[545]]

The systematic position of the genera Hislopia and Norodonia,[^[546]] which have been described from fresh water of India and China respectively, is at present uncertain. The undoubted Cheilostome Membranipora has, however, a British representative (M. monostachys), which occurs in brackish water, in ditches on the coast of East Anglia. It is there known to form "friable, irregularly-shaped, sponge-like masses," which grow on water-plants.[^[547]]

The Entoprocta, as we have seen, are represented in fresh water by the genus Urnatella.

The Phylactolaemata are an exclusively fresh-water group, and they are believed by Kraepelin[^[548]] to have been derived from the Ctenostomata. Many of their special peculiarities can, with great probability, be regarded as adaptations to a fresh-water existence. This is particularly clear in the all but universal habit of dying down in the winter, and in the occurrence of the so-called statoblasts (Fig. 251), which are hard-shelled reproductive bodies, absolutely restricted to the Phylactolaemata, and capable of resisting the winter's cold and even a certain amount of drying up. Phylactolaemata have indeed been recorded from the tropics; but it is not yet sufficiently clear how they there behave in these respects. F. Müller[^[549]] has found these animals in Brazil, where they are said to be more common at certain periods of the year than at others. Stuhlmann has found them in Tropical Africa (Victoria Nyanza, etc.);[^[550]] and Meissner[^[551]] has discovered the sessile statoblasts of Plumatella on the shells preserved in the Berlin Museum, of species of the Mollusc Aetheria from various localities in Africa. Fresh-water representatives of a considerable number of other groups of animals agree with the Phylactolaemata in the possession of reproductive bodies which are protected by hard coats. Such, for instance, are the ephippian ova of Daphnia—bodies which have an extraordinary external similarity to statoblasts—the gemmules of Spongillidae, the winter-eggs of Rhabdocoels and Rotifers, and the cysts of Protozoa. The evolution of these bodies in so many widely different cases may have been due to the selection of variations calculated to minimise the dangers attendant on the drying up of the water in summer, or on its freezing in winter.

The Phylactolaemata are by no means uncommon, although they can seldom be found without a careful search. Their presence may often be detected by taking advantage of the property of the free statoblasts of rising to the top of the water, where they can be discovered by skimming the surface with a fine hand-net.

The colonies themselves are usually found attached to water-plants, roots of trees or stones. Most of them flourish best in a zone not more than two feet below the surface. Certain species show a preference for floating leaves, such as those of water-lilies, where they are not liable to be dried up by alterations in the level of the water. Some forms (e.g. Plumatella, Fig. 246) are, however, able to withstand being dried for some time. Most species prefer shady places, and accordingly settle on the lower sides of leaves and sticks. Others (e.g. Cristatella, Fig. 247) have no objection to the direct rays of the sun. Most forms prefer still water, but one or two are found in running water.

Fredericella is a common constituent of the deep-water fauna of Swiss Lakes (down to over forty fathoms); and reaches there a size considerably larger than the shallow-water form of the same species. Paludicella is common at thirteen fathoms. These two genera, with Plumatella, have been found in absolute darkness, under a pressure of 2½-5½ atmospheres, in the Hamburg aqueduct. The Polyzoa and other organisms growing in the water-supply of Hamburg were accused of being concerned in the spreading of cholera, during the recent epidemic, by choking up the water-pipes, and creating obstructions which formed a favourable nidus for the development of cholera-germs.

The colony may take the form of a series of delicate, branching tubes (Plumatella, Fredericella), of more massive aggregations of parallel tubes (as in the Alcyonelloid forms of Plumatella), or of gelatinous masses of varying size (Lophopus, Cristatella).

Fig. 246.—A, Plumatella (Alcyonella) fungosa Pall., Naples (fresh water), small part of a mass, natural size; B, Plumatella repens L., R. Yare, on the leaf of a water-lily, natural size.

Cristatella mucedo (Fig. 247) is remarkable for its power of moving from place to place; it consists of an elongated mass of greenish, gelatinous substance, which, in its fully developed state, may reach a length of eight inches or more, with a transverse diameter of three-eighths of an inch. It has a flattened sole on which it crawls, while the graceful plumes of its numerous polypides protrude as a delicate fringe from its upper side.

The tentacles are about eighty to ninety in number, and they are, as in other Phylactolaemata, united at their bases by a delicate web. The lophophore is horse-shoe-shaped (Fig. 236, 3) throughout the group, with the exception of Fredericella, in which genus it is circular.

In some Phylactolaemata the polypide has been observed to interlace its tentacles, so that the plume becomes a kind of cage, in which the more active Infusoria are imprisoned until their struggles have so far weakened them that they are swept into the mouth by the action of the cilia of the tentacles.[^[552]]

Fig. 247.—Cristatella mucedo Cuv. (a small colony), R. Yare, above Norwich, × 24.

Around the edge of the Cristatella is found a zone of budding tissue, which gives rise continuously to new individuals. Now, whereas in Gymnolaemata the growing edge gives rise to zooecia, whose cavities become completely cut off from that of the older ones; in Phylactolaemata the partitions between the zooecia are never completed. The body-cavity of Cristatella is thus a continuous space, interrupted at the margin only by vertical septa (see Fig. 247), which represent the partitions between the zooecia of other forms.

The body-wall consists of two epithelial layers of ectoderm and mesoderm, between which is a layer of muscular fibres. Parts of the epithelium lining the body-cavity are ciliated. Into the common body-cavity hang the polypide-buds at the edge of the colony, and the mature polypides in the more central regions. There are usually three rows of polypides on either side of the middle line, in the neighbourhood of which is an area devoid of polypides, but containing "brown bodies" and statoblasts. The polypides nearest to the middle line pass in succession into the condition of "brown bodies," while young buds near the margin grow up coincidently to form new polypides.

The movement of the colony is in the direction of the long axis, although either end may go first. Sir John Dalyell records an observation[^[553]] on a specimen (about one inch long) which was artificially divided into two halves. The two halves "receded from each other as if by common consent," and were nearly an inch apart in twenty hours.

An observation made at Cambridge on a small colony of about 7 mm. in greatest length gave the following results. The colony moved 13 mm. (nearly twice its own length) in 8¼ hours: in the next 40 hours it moved 20 mm. (⅘ inch); while in the following 24 hours it moved only 6 mm. Large colonies change their place only with reluctance.

The locomotive power possessed by Cristatella is not unique among Phylactolaemata. Lophopus, the first fresh-water Polyzoon of which any description was published, was originally described by Trembley in 1744 under the name of the "Polype à pannache." Trembley observed the spontaneous division of the colony, followed by the gradual separation from one another of the daughter-colonies.[^[554]] The power of dividing spontaneously is also possessed by colonies of Cristatella and of Pectinatella.

The colonies of Lophopus are surrounded by an excessively hyaline ectocyst, and are usually triangular, as shown by Fig. 248. When division is about to occur, the base of the triangle becomes indented, and the indentation travels towards the apex in such a way as to bisect the triangle. The two halves diverge from one another during the process, so that before division is complete, they are looking, in some cases, in opposite directions. After a time the narrow connection breaks, and two new colonies are formed.

Fig. 248 shows a colony shortly after division has taken place. The colony had moved forwards, in a direction away from its apex, for three days in a nearly straight line, the distances moved in each day being respectively 6, 8½, 8½ mm. These observations, for which I am indebted to Mr. Lister, show a considerably higher speed than in those recorded by Trembley, who observed no colony which moved more than half an inch (12.5 mm.) in eight days.

The genus Pectinatella also has some power of locomotion. This magnificent Polyzoon occurs in masses several feet in length (as much as six feet in P. gelatinosa from Japan[^[555]]), and four to eight inches in thickness. The greater part of P. magnifica[^[556]] consists of a thick, opaline, and gelatinous ectocyst, the upper surface of which is covered by hundreds of rosette-like colonies, which increase in number by division. The masses are thus aggregations of colonies, which secrete a common basal ectocyst. The latter decays in the autumn; and the separate rosettes, or groups of them, may thus be set free, being found as floating masses, which may again attach themselves to a solid object till the time of their death. Pectinatella has not yet been recorded in England, although, considering the ease with which statoblasts are transported, it is by no means improbable that it will eventually be recorded as a British genus. It is at present known to inhabit America, Japan, and Hamburg.

Fig. 248.—Lophopus crystallinus Pall., Cambridge, showing the rate of movement. The colony and the distances moved are × 2.

It is by no means certain what is the mechanism by which movement takes place in the above cases. The ectocyst of Cristatella is confined to the base of the colony, and there forms a thin slimy film, which lubricates the surface over which the animal moves. It has been stated[^[557]] that progression is produced in the following way. The polypides are withdrawn by means of retractor muscles, which originate from the septa and inner surface of the sole. Thus at each retraction of any polypide, the muscle pulls on a portion of the sole. Should the expanded polypides place themselves in a suitable position, the movement will be in the direction of the resultant of the forces due to the separate retractor muscles; while it is probable that their cilia assist in the onward movement. It should be noted that it is definitely stated that a colony in which all the polypides are retracted can alter its position,[^[558]] although even then the retractor muscles might still contract to some extent.

The movement probably depends on several causes. It must probably be conceded that the sole itself has some effect on this process. Its outer cells are contractile, and have the power of raising themselves from the underlying ectocyst. They may then again attach themselves, and this new attachment does not always take place in exactly the same place as the former one. Any movement of the muscles of the sole, or of the retractor muscles, will thus shift the skin to a new place.[^[559]]

Protrusion of the Polypide.—While it is perfectly clear that retraction is principally performed by the great retractor muscles acting directly on the polypide, it is less easy to explain the converse movement. There can, however, be little doubt that protrusion is effected by the pressure of the fluid of the body-cavity, caused in large part by contractions of the common body-wall.

Now since, in Cristatella, the body-cavity is a continuous space, any pressure on the fluid must act uniformly on all its contents. The cause which determines the protrusion of a polypide is thus to a large extent the relaxation of the sphincter-muscle which surrounds its orifice, aided by special muscles which dilate the orifice. Any polypide which is retracted while the pressure of the fluid in the body-cavity is sufficient to keep other polypides protruded, must therefore keep either its retractor-muscles or its sphincter in a state of contraction in order to remain in that position. And as a matter of fact, Cristatella and Lophopus differ from most other Polyzoa in the readiness with which they expand their tentacles, after they have been induced to retract themselves by mechanical irritation.

Plumatella and other forms have a chitinous ectocyst, which, however, is sticky when it is first formed. By virtue of this property, the branches become attached to the leaf on which the colony is growing, and may have their natural transparency obscured by taking up foreign bodies. The stiffness of the ectocyst naturally involves some modification of the process by which the polypides are protruded. In some cases, this is effected by the separation of the endocyst from the ectocyst in the lower parts of the tube. The muscles of the body-wall can thus press on the fluid of the body-cavity without being restrained by the inflexible ectocyst. In other cases, the tube of ectocyst is rendered flexible by the presence of a thin line along one side where the chitin is deficient.

Fig. 249.—Plumatella repens L., R. Yare, × 30. a, Anus; b, polypide-bud; c, caecum of stomach; d, duplicature; e, epistome (see p. [476]); f, funiculus; g, ganglion; m, retractor muscle; p, parieto-vaginal muscles; ph, pharynx; s, statoblasts attached to f.

The upper end of the retracted tentacle-sheath is connected with the body-wall by bands known as the parieto-vaginal muscles (Fig. 249, p). These serve not only to dilate the orifice when protrusion is commencing, but also to prevent the polypide from being forced out too far. They are arranged in such a way that a circular fold, the duplicature (d), is never turned inside out, even in the state of complete protrusion of the polypide.

The mechanism of the protrusion of the polypide in the Gymnolaemata is in many cases obscure. The body-wall is not muscular in this group, in some forms of which, however, short strands known as the parietal muscles (Fig. 234, p) pass across the body-cavity from one point to another of the zooecium. As doubts have been thrown on the function of these muscles in causing protrusion, it will be worth while to refer to the detailed and convincing statements of Farre,[^[560]] relating to this point.

Farre's observations were made on certain transparent Ctenostomes (Bowerbankia and Farrella). He states that the parietal muscles "were distinctly seen to contract whenever the protrusion of the animal took place, and to become relaxed again upon its retiring into its cell." Their contraction may indent the outline of the ectocyst, or may cause the separation of the endocyst from the ectocyst. The endocyst is then drawn into longitudinal lines at the origin and insertion of these fibres. It is further suggested that some part is played in the process by the muscular walls of the alimentary canal, which is a good deal bent in the retracted condition. The effort to straighten itself is believed to have some share in forcing out the polypide. The flexible, membranous character of the "aperture" (see p. [524]) in Membranipora (Fig. 256, A) is said by Nitsche[^[561]] to be an arrangement for the protrusion of the polypides; the parietal muscles passing from the lateral walls of the zooecium to the upper membranous wall, which is accordingly depressed by their contraction.

Although it is hardly possible to doubt the accuracy of Farre's observations, which have, moreover, been confirmed by Hincks, it is by no means certain that this is the whole explanation in all cases. Oka,[^[562]] for instance, states that protrusion of the polypide in Phylactolaemata can be effected in a branch whose body-wall has been cut open. Pergens[^[563]] believes that the diaphragm (Fig. 234, d) acts as a pump, introducing water from the tentacle-sheath into the body-cavity, into which it is said by him to open, and so forcing out the polypide. It is probable that many of the forms which have a stiff, unyielding ectocyst possess special arrangements for introducing water in some way into the space bounded by the ectocyst,[^[564]] and so forcing out the polypide. Such, for instance, may be the median pore which occurs beneath the orifice in Microporella (Fig. 241, A, mp), and in certain other cases.

Reproduction of Phylactolaemata.—Sexual reproduction takes place in Cristatella from June to August. The spermatozoa are ordinarily produced on the funiculus. The ovaries usually occur on the inner side of the common wall of the colony, not far below the orifice of a polypide. Each ovary matures a single egg, which develops in situ, the free larva leaving the colony by the orifice of one of the degenerated polypides.

A second method of reproduction takes place by means of the statoblasts, which are developed on the funiculus (Fig. 249). According to Verworn,[^[565]] each statoblast arises from a single cell of the funiculus; and on this view, the statoblast is, as supposed by the earlier observers, a special kind of winter-egg. According to more recent researches,[^[566]] the funiculus consists of a central axis, formed from the ectoderm, and of an outer sheath of mesoderm-cells; the statoblast is developed from the two kinds of cells of which the funiculus is composed, and is consequently comparable in its mode of origin to an ordinary bud. Its special peculiarities are: its origin as an internal bud, its possession of a chitinous shell, and the fact that it is destined to leave the parent colony, and to develop, after a period of rest, into a new colony. Germination takes place by the formation of a polypide-bud inside the statoblast, which finally splits along its equator into two halves. The contents emerge as a young colony which possesses at least one fully-formed polypide.

Remarkable structures known as "hibernacula" occur in the fresh-water Ctenostomes, Paludicella and Victorella. These bodies are in the former (Fig. 250, B) specially modified external buds, which persist through the winter when the rest of the colony dies down. At the close of winter the shell splits into two halves, exactly as takes place in the statoblasts, and a young colony emerges. It is possible that the statoblasts may have been evolved from a hibernaculum, which was at first produced externally, but has become modified in such a way as to acquire an internal mode of origin.[^[567]]

The simplest known statoblast is that of Fredericella (Fig. 251, A), which differs from that of other Phylactolaemata in having no ring of air-cells. In Plumatella, the statoblast (Fig. 251, B) has a broad equatorial ring of air-cells, which enable it to float at the surface of the water on the decay of the parent tubes. In some species, certain statoblasts which are produced in the adherent parts of the colony remain attached to the substratum. These "sessile statoblasts" may have no trace of the ring of air-cells; but the fact that many sessile statoblasts have rudiments of this structure suggests that they are a secondary modification of the floating statoblast. In Lophopus (Fig. 251, C) the ring of air-cells is very broad, and is pointed at each end; while in Cristatella (Fig. 251, D) and in Pectinatella the statoblast is circular, and possesses an armature of hooked spines. That of Cristatella, measures about .75 mm. in its greatest length.

Fig. 250.—Paludicella ehrenbergi van Beneden, × about 3. A, Part of a colony with expanded polypides; B, remains of part of a colony which has produced hibernacula or winter-buds (h); z, zooecium. (From Kraepelin.)

Kraepelin has suggested that the above order of increasing complexity of the statoblasts corresponds with the order in which the genera to which they respectively belong would be placed, on the assumption that the Phylactolaemata have been derived from the Ctenostomata. Thus, in Fredericella, the form of the lophophore is circular, as in the Gymnolaemata. The number of the tentacles is comparatively small (20-24). The arborescent form of the colony resembles that of many Ctenostomes, and the zooecia are more or less cut off from one another by incomplete septa.

In Plumatella, the lophophore has become horse-shoe-shaped, and the tentacles are more numerous (38-60). In general form and in the arrangement of the septa this genus resembles Fredericella, with which it may easily be confused.

In Cristatella we have the most highly modified of all the Phylactolaemata. The individuality of the zooecium is here subordinated to that of the colony as a whole. The branched arrangement of the zooecia is greatly obscured. The body-cavities have become completely confluent, although rudiments of the septa still exist. The ectocyst has been lost, with the exception of the basal layer of the colony. The tentacles are more numerous (80-90); and in accordance with the increase in the elaboration of the genus, its statoblasts belong to the most complicated type known.

Fig. 251.—Statoblasts of Phylactolaemata. A, Fredericella sultana Blum., × 38; B, Plumatella repens L., × 38; C, Lophopus crystallinus Pall., × 28; D, Cristatella mucedo Cuv., × 28. (A, from Allman; B-D, from Kraepelin.)

The production of floating statoblasts may seem a strange adaptation to the conditions of fresh-water life, since it might be assumed, a priori, that these structures would be specially liable to be frozen during the winter. The following experiments made by Braem[^[568]] show, however, that the germinating power of the statoblasts is improved by a certain amount of frost. A number of statoblasts were taken; half of these were placed in water, which was then frozen; and these were found to germinate readily when afterwards exposed to suitable conditions. The other half were not subjected to the action of frost; and these could not be made to germinate, even although the water had been cooled to a point slightly above the freezing point. It thus appears that the buoyancy, so far from being a risk, is a means of exposing the statoblast to the conditions which are most favourable to its later development.

Braem supposes that the beneficial action of frost is due to a lowering of the vital energy of the statoblast. As in the case of reproductive bodies known in many other fresh-water organisms, the statoblast germinates only after a period of rest. Although this period is often shortened by a lowering of the temperature, it can also be induced by the exclusion of air, as in an experiment during which the statoblasts were enclosed in airtight tubes. The respiratory processes were thereby lessened, and the germinating power was materially improved.

Since the development of the statoblasts depends largely on the temperature, the first warm weather in early spring will probably induce the germination of those which are floating; and the young colony, leaving the protection of the statoblast, will become susceptible to frost. But even if the first-formed colonies are killed off by a subsequent frost, other statoblasts which have remained in the mud during the winter are disentangled from time to time, and germinate on reaching the surface.

Distribution.—The protective value of the shell is also shown by the fact that the statoblast may be kept for some months in a dry condition without losing its power of germination. There can be little doubt that the capability of withstanding desiccation enables the species to enlarge its area of distribution. It is asserted that fresh-water Polyzoa decrease in abundance in proportion to the distance from the mouth of the river in which they are found. The current will naturally tend to bring together the statoblasts from the Polyzoa growing in the upper waters.

Nothing is more surprising than the wide geographical distribution of the Phylactolaemata. The European genera are all recorded from North America. Fredericella, Plumatella, and Lophopus are further recorded from Australia; while Plumatella is known to occur also in Malacca, the Philippine Islands, India, Japan, Africa, and South America, It is even stated that some of the Australian species are identical with those found in Europe.

Some of the fresh-water Polyzoa are extremely variable, and observers are by no means agreed in deciding whether certain well-known forms are to be regarded as varieties or as species. While certain genera, such as Cristatella and Lophopus, are comparatively constant in their form, Plumatella is excessively variable. Plumatella has a number of species greater than that of any other form, and the genus has a wider distribution than any other. This greater variation of species of the dominant genus is in complete accordance with the general law enunciated by Darwin that "wide-ranging, much diffused, and common species vary most."

While the ordinary forms of Plumatella consist of branching colonies, which are either completely adherent to their substratum, or grow in a more or less erect manner, another habit which is assumed by this genus is so different from the first that it has been considered to mark a distinct genus, Alcyonella. The Alcyonelloid form (Fig. 246, A) consists of closely packed tubes which stand more or less at right angles to their substratum, which they may cover with a dense mass an inch thick, and with a superficial area of several square inches. But in spite of this difference, it is possible that A. fungosa is only a variety of an ordinary Plumatella form. Whether this is so or not, a typical Plumatella may in places take on an Alcyonelloid habit; and parts of an Alcyonella may become so lax in growth as to resemble a Plumatella.

The British genera of fresh-water Polyzoa may be distinguished from one another by means of the following table:—

1.		Zooecia perfectly distinct from one another. Lophophore circular. Statoblasts absent 2
		Colony formed of branching tubes composed of confluent zooecia 3
		Colony gelatinous, not obviously formed of branching tubes. Lophophore horse-shoe shaped 4
2.		Colony consisting of a stolon from which new zooecia originate. These may give rise to new stolons, or directly to new zooecia Victorella
		Branches composed entirely of club-shaped zooecia, each of which may give off two zooecia near its upper end Paludicella (Fig. 250)
3.		Tubes hyaline or opaque, usually containing numerous oval statoblasts (Fig. 251, B), most of which have a ring of air-cells. Lophophore horse-shoe shaped.
		(a) Tubes divergent Plumatella (Fig. 246, B)
		(b) Tubes parallel with one another Alcyonella form of Plumatella (Fig. 246, A)
		Tubes cylindrical, usually dark brown. Statoblasts (Fig. 251, A) few, without air-cells. Lophophore circular Fredericella
4.		Colony hyaline, usually divided into three or four short lobes. Ectocyst thick. Statoblasts (Fig. 251, C) pointed at each end, with a broad ring of air-cells Lophopus (Fig. 248)
		Colony slug-shaped, crawling on a flattened sole. Ectocyst rudimentary. Statoblasts (Fig. 251, D) circular, with marginal hooks Cristatella (Fig. 247)
		Colonies consisting of small rosettes, many of which are attached to a thick basal layer of hyaline ectocyst. Statoblasts circular, with marginal hooks. (Not recorded as British) Pectinatella

Reproductive Processes of Polyzoa in general.

In studying the reproductive processes of Polyzoa, we have to deal with two very distinct phenomena; firstly, with the development of eggs; and secondly, with the formation of buds.

The process of budding usually does no more than increase the number of individuals in a colony which already exists, and is seldom responsible for the commencement of a new colony. In Loxosoma, however, the buds break off and lead an independent existence; and in the Phylactolaemata a large proportion of the colonies have their origin in the statoblasts. In certain cases, again, new colonies may be formed by the detachment of parts of an old one, as by the fission of Cristatella and Lophopus, or by the breaking up of a richly-branched species into several colonies by the decay of the proximal parts.

We may then in the majority of cases look to an embryo for the foundation of a new colony. The embryo develops into a larva, which, after a period in which it swims freely, settles down, and is metamorphosed into the first zooecium. This primary individual forms the starting-point of a colony, and often differs to a considerable extent from the other zooecia which arise from it. In Cyclostomata, for instance, the proximal end of the primary zooecium permanently retains the disc-like shape assumed by the young larva when it first fixed itself. The primary zooecium may be recognised with equal ease in many Cheilostomata, and may differ from its successors by possessing a richer development of marginal spines, or in other respects.

Reproductive Organs.—Eggs and spermatozoa are commonly found in the same colony, either in different individuals, or else in the same zooecium (see Fig. 234, p. [469]). In some cases, the zooecium first develops spermatozoa, and later eggs. The Entoprocta have a more marked separation of the sexes than obtains in other Polyzoa. The genus Loxosoma is perhaps always dioecious (i.e. with separate sexes). Pedicellina is sometimes found with ovaries and testes in the same individual, sometimes with these organs in different individuals; and it is not clear whether a given species always behaves alike in these respects.

The reproductive organs of the Entoprocta open by ducts of their own into the vestibule. In the Ectoprocta they are developed in the body-cavity, and they have no ducts.

The fate of the ripe egg differs widely in different cases. In the Entoprocta it develops in a kind of brood-pouch formed from part of the vestibule. The fact that in Pedicellina (Fig. 243) the embryos grow largely during their development, shows that nutritive material must be supplied to them from the parent. There is reason to believe that the epithelium of the brood-pouch is responsible for this process. The eggs are also known to develop at the expense of nutritive substances prepared by the parent in the ovicells of the Cyclostomata. In other cases, as in some species of Alcyonidium, the egg is large, and its copious yolk doubtless supplies a large part of the material required for development.

In the Ectoprocta, development takes place in a variety of places. In most Cheilostomata a single egg passes into the globular ovicell, which is formed above the orifice of many of the zooecia. In certain Ctenostomata,[^[569]] Phylactolaemata,[^[570]] and Cyclostomata,[^[571]] the ripe egg is taken up by a rudimentary polypide-bud, which is specially formed for the purpose. In the Ctenostomata and in the fresh-water Polyzoa these buds, if present, are found in ordinary zooecia which do not become modified externally in any special way. In the Cyclostomata (Crisia), on the contrary, the formation of the polypide-bud is intimately bound up with the development of the ovicell. The number of the zooecia which produce eggs that are capable of development is greatly restricted in this group. The ovicell, which contains numerous embryos, is not merely a portion of a zooecium, as in the Cheilostomata; but it is probably to be regarded as a modification of the entire fertile zooecium or zooecia. These take on an appearance widely differing from that of the ordinary zooecia, and in course of time give rise to the ovicells (see Fig. 237).

In all these cases the egg develops inside the parent, and it was hardly known, before the publication of the interesting researches of M. Prouho,[^[572]] that some of the Polyzoa lay eggs which develop externally. In these cases a considerable number of eggs are produced simultaneously by a single zooecium. M. Prouho further throws light on a much contested subject; namely, the nature of the so-called "intertentacular organ" (i, Fig. 234, p. [469]), described so long ago as 1837 by Farre,[^[573]] but looked for in vain by the majority of later observers.

The failure to find this organ, even in species which possess it, in certain individuals, according to Farre's statements, is now satisfactorily explained by M. Prouho, who shows that while it is absent in a large number of polypides, it is normally present in those individuals which possess an ovary, and in those only; and that its primary function is that of an oviduct.

The intertentacular organ is an unpaired ciliated tube, which is situated between the two tentacles which are nearest to the ganglion. In the retracted condition of the polypide, it opens from the body-cavity into the tentacle-sheath; and in the expanded condition, directly to the exterior.

In the remarkable case of Alcyonidium duplex, each zooecium normally possesses two sexual polypides. The first of these produces a testis and then becomes a "brown body." The second is meanwhile developed, and produces an ovary and an intertentacular organ, a structure which was not present in the male polypide. The eggs pass through the intertentacular organ into the tentacle-sheath, and attach themselves to the diaphragm (d, Fig. 234), where they remain during their development.

Although the intertentacular organ has been found by Prouho in female polypides only, it would perhaps be going too far to assert that it is confined to polypides of that sex. Hincks[^[574]] has observed the passage of spermatozoa in enormous numbers through the organ, although it may be noted that there is no sufficient proof that eggs were not present as well in these zooecia. It further appears that in some cases waste matters may be removed from the body-cavity through the same passage.

It may be presumed that the egg is normally fertilised by a spermatozoon, although this is at present largely a matter of inference. It is believed by Joliet[^[575]] that fertilisation is reciprocal, although Prouho has come to the opposite conclusion. Joliet has, however, very justly pointed out that the enormous number of spermatozoa developed by a single individual would be disproportionately large, if their function were merely to fertilise the ovum in the same zooecium. According to his view, the egg is fertilised by a spermatozoon after it has passed into the tentacle-sheath or ovicell, or some other place where it is in free communication with the outside water.

Development and Affinities.—Few parts of the history of the Polyzoa are more fascinating than that which deals with their development; and it is probable that no other is capable of giving so much insight into the affinities of the several groups to one another and to other groups of the animal kingdom.

Fig. 252.—Diagrams of larvae. A, Loxosoma, × 208; a, anus; b, brain, with left eye and ciliated pit; c, ciliated ring; ep, epistome; m, mouth; o, oesophagus; st, stomach; x, aboral adhesive organ: B, Cyphonautes larva of Membranipora (Electra) pilosa, × about 90; a, m, o, st as in A; c, anterior part, and c', posterior part of the ciliated ring; e, epidermis; ms, adductor muscle of shells; p, pyriform organ, of unknown function; sh, shell; v, vestibule; the "internal sac" or sucker, by which fixation is effected, is seen between a and ms. (B, after Prouho.)

The comparative study of the larvae of the Polyzoa may be said to date from 1877, when J. Barrois published an elaborate Monograph[^[576]] on this subject. Although some of Barrois' earlier opinions have been subsequently modified, this work still gives the best figures of the external form of the beautiful larvae of many genera. A detailed account of the larval forms of Polyzoa must be omitted from want of space; and the general conclusions only can be given.

The larvae of the Entoprocta (Fig. 252, A) resemble the so-called "Trochosphere" of Polychaeta (see p. [274]). The common characters shared by the larvae of Chaetopoda, Echiuroid Gephyrea, Mollusca, and Polyzoa, and by adult Rotifera, may well point to the derivation of these groups from a common ancestor. On this assumption, it is possible that the Polyzoa have been derived from forms which existed long ages ago, which combined the common characters of these groups, and the structure of which we can picture to ourselves only so far as the "Trochosphere" larva can be taken to represent it in a much simplified condition. Such a view harmonises well with the great antiquity of the Polyzoa. Certain Ectoproct forms have a larva, known as Cyphonautes (Fig. 252, B), which closely resembles the larval form of the Entoprocta; and it is a fact which probably has considerable significance that this type of larva is known to occur only in those species of Membranipora (Electra), Alcyonidium, and Hypophorella, which lay eggs.[^[577]] This may perhaps be regarded as a primitive form of development which has been lost in species in which development takes place inside the parent. Cyphonautes compressus (Fig. 252, B), one of the commonest objects taken in the surface-net off our own coasts, is the larva of Membranipora (Electra) pilosa. Whilst this larva is provided with a well-developed alimentary canal, those of most other Ectoprocta possess a mere rudiment of this structure, and depend for their nutrition either on yolk present in the egg or on material supplied by the parent. In most cases the mature larva has no recognisable trace of a digestive system; and, although it has a free-swimming period, it does not become truly pelagic.

The alimentary canal of the larva of Pedicellina is known to persist in the primary individual of the colony. In all other known cases, even in that of Cyphonautes, the larva at fixation loses practically all its internal organs, and becomes a mere body-wall containing a mass of degenerated larval tissues. It is in fact a zooecium containing a "brown body." A polypide-bud is now developed, the body-cavity appears as the result of the shrinkage of the "brown body," and the primary individual of the colony is thereby established.

The larvae of the Ectoprocta form a tolerably complete series, starting from Cyphonautes, itself allied to the larva of the Entoprocta, and ending with the Phylactolaemata. Alcyonidium (Fig. 253, B) possesses a rudimentary alimentary canal,[^[578]] although the most conspicuous structures are those connected with the fixation and other phenomena of larval life. The larvae of many of the encrusting Cheilostomes (Fig. 253, A) resemble that of Alcyonidium, while those of Bugula, Scrupocellaria, etc., belong to a type easily derivable from that of the encrusting forms. The branching Ctenostomes (Bowerbankia, etc.) have a larva which may be regarded as derived, along slightly different lines, from that of Alcyonidium. The Cyclostomata and the Phylactolaemata have the most modified forms of larva. That of the former group may owe some of its peculiarities to the occurrence of a remarkable process of embryonic fission, which takes place in the ovicell, and as the result of which each egg gives rise to a large number of larvae.[^[579]] The Phylactolaemata have a larva which is not unlike that of Bowerbankia.

Fig. 253.—A, Aboral view of free larva of Lepralia foliacea Ell. and Sol.; a, long cilia of pyriform organ; g, aboral groove: B, longitudinal section of embryo of Alcyonidium, × 135; c, ciliated ring; g, aboral groove; m, mouth; n, nervous system; p, "pyriform organ," of unknown function; s, "internal sac" or "sucker," by which fixation is effected; st, stomach.

We have seen that the larva at fixation becomes a zooecium, which in the Gymnolaemata forms a polypide-bud after fixation. The peculiarities of the Phylactolaematous larva may be explained by assuming that it becomes a zooecium while it is still free-swimming. Thus the larva of Plumatella develops one or sometimes two polypides, which actually reach maturity before fixation takes place. That of Cristatella develops from two to twenty[^[580]] polypides or polypide-buds at the corresponding period, and it is in fact a young colony while still free-swimming.

Now in most colonial animals, such as Coelenterates and Ascidians, the larva metamorphoses itself into a temporarily solitary animal, which then gives rise to the remainder of the colony by budding. The majority of the Gymnolaemata behave in this way; while the Phylactolaemata may not only develop a multiplicity of polypides in their larval stage, but the individuality of the zooecia is then just as much obscured as in the adult state. These facts are more easily explained if we assume that Cristatella is the end-point in a series than if we suppose it to be a starting-point.

On the view maintained by many authorities, that the Polyzoa are related, through Phoronis, with the Gephyrea and the Brachiopoda, we should expect to find in those Polyzoa which most closely resemble Phoronis in their adult state—that is to say in the Phylactolaemata—some indications of affinity to that animal in their development. This is emphatically not the case. The hypothesis that the Phylactolaemata are related to Phoronis leads, moreover, to the improbable conclusion that the similarities between the Entoproct-larva and Cyphonautes, on the one hand, and the Trochosphere larva of Polychaeta, on the other hand, is entirely superficial and meaningless. In spite, therefore, of the similarity between Phoronis and a single individual of the Phylactolaemata, and in spite of the marked resemblance between its nephridia and structures which have been described in Cristatella[^[581]] and Pectinatella[^[582]] the comparative study of the development appears to indicate that the resemblances between Phoronis and the Phylactolaemata are the result of a coincidence rather than of any close relationship.

A few points connected with the metamorphosis of the Polyzoa deserve more special notice. There is generally great difficulty in persuading larvae to fix themselves when kept in a small quantity of water, which becomes over-heated in the air of a laboratory. The difficulty may be surmounted by placing colonies containing embryos, together with some clean pieces of the seaweed on which the adults are habitually found, in a vessel closed by a piece of fine muslin, and by leaving the vessel attached to a buoy or in a deep tide-pool. The larvae being without an alimentary canal, fix themselves, after a very short free life, on the seaweed.

It is probable that a great struggle for existence normally takes place at the commencement of the metamorphosis. Any one who will examine, in June or July, rocks covered by Fucus on which Flustrella hispida is growing, will probably find numerous young fronds of Fucus, from half an inch to an inch or two in length, growing under the shelter of the older fronds. The bivalve larvae of Flustrella show a marked preference for fixing on these young fronds—perhaps in order that the duration of life of the colony may coincide with that of the Fucus—and these young fronds are commonly covered by very numerous recently-fixed larvae, and by young colonies of various ages. Or, it is easy to observe, by placing pregnant colonies of Bowerbankia in a vessel of water, that the larvae, which are hatched out in thousands, fix themselves in dense masses on certain parts of the wall of the vessel. It is clear that but a small proportion of these larvae will find room for further development.

Next with regard to the mode of fixation. Attachment always takes place by the surface on which the mouth or its rudiment is situated, and the permanent alimentary canal opens on the opposite surface. In Pedicellina, the one case in which the larval digestive organs are known to become those of the first adult individual, this presupposes a rotation of the alimentary canal, in order to bring it into its new position.

It is well known that the larvae of other fixed animals may undergo a somewhat similar change. Thus those of Ascidians and of Barnacles fix themselves by their anterior end, and ultimately reach their adult form by performing a kind of a somersault. The process may perhaps be explained by supposing that some part of the anterior end or of the oral surface is specially sensitive, and that the larva fixes itself by that portion of its body which is best fitted for ascertaining which is the proper substance on which to fix.

Budding.—The formation of a new individual may take place by the outgrowth of part of the body-wall, as in Pedicellina (Fig. 243, p. [487]) and in Bowerbankia (Fig. 238, p. [480]). In Pedicellina a young stalk is formed by an outgrowth near one of the growing points, and the upper part of this outgrowth becomes constricted off to form the calyx. In other cases (cf. the growing ends of the branches in Fig. 237) a partition grows across the body-cavity at the growing edge of the colony, and so cuts off a part destined to become a new zooecium.

The zooecium formed in one of these ways acquires an alimentary canal by the formation of a polypide-bud, some stages in the growth of which are shown in Fig. 235 (p. [472]). Contrary to what happens in Coelenterates and Tunicates, in which the endoderm takes part in the budding, there is good reason for believing that in Polyzoa the polypide-bud is developed entirely from ectoderm and mesoderm.[^[583]] The bud is a two-layered vesicle, attached to the inner side of the body-wall. Its inner layer is derived from the ectoderm, which at first projects into the body-cavity in the form of a solid knob surrounded by mesoderm-cells. A cavity appears in the inner, ectodermic mass, and the upper part of the vesicle so developed becomes excessively thin, forming the tentacle-sheath, which is always developed in the condition of retraction. The lower part becomes thicker; its inner layer gives rise to the lining of the alimentary canal, to the nervous system, and to the outer epithelium of the tentacles, which grow out into the tentacle-sheath (cf. Fig. 235). The outer layer gives rise to the mesodermic structures, such as the muscles, connective tissue, and generative organs.

These processes are fundamentally similar, whether in the metamorphosed larva, in a young zooecium, in an old zooecium after the formation of a "brown body," or in the germinating statoblast of the Phylactolaemata.

CHAPTER XIX

POLYZOA (continued)

CLASSIFICATION—GEOGRAPHICAL DISTRIBUTION—PALAEONTOLOGY—METHODS FOR THE EXAMINATION OF SPECIFIC CHARACTERS—TERMINOLOGY—KEY FOR THE DETERMINATION OF THE GENERA OF BRITISH MARINE POLYZOA

Our account of the Polyzoa would be manifestly incomplete without some reference to the systematic arrangement of these animals. An outline of the principal groups has been given on p. [475]. So far, the classification is easy, but it is otherwise when we attempt to subdivide most of the groups any further.

Systems of classification which depend exclusively upon the external characters of animals have been repeatedly shown to be unsatisfactory. Now with regard to the Polyzoa, not only is it the case that the great majority of forms are only known in their external characteristics, but current systems of classification cannot be regarded as final, because it is not yet certain which of the external features have most systematic value. Two obvious points can be at once selected—namely, the character of the zooecium and the character of the entire colony. One or two instances will serve to show what different results are obtained by depending exclusively on either of these characters by itself.

According to the older writers, the habit of the colony was taken as the most important generic character; and there can indeed be no doubt that this feature has great importance within certain limits. Any one who has examined different species of such genera as Flustra, Cellaria, Bugula, Retepora, etc., must feel that the form of the colony goes for a good deal. But a consideration of other cases shows that there is great risk in the indiscriminate use of this method of arranging the Polyzoa. The old genus Eschara, composed of forms with an erect coral-like habit,[^[584]] included species which are now placed in such different genera as Lepralia, Porella, Microporella, etc. The older works on Polyzoa include all encrusting forms of Cheilostomata, with a completely calcareous front wall, in the genus Lepralia, the members of which are now distributed in numerous widely separated genera.

As an instance of the converse arrangement—essential similarity of the zooecia with great differences of the general habit—may be mentioned the common Membranipora (Electra) pilosa.[^[585]] Ordinarily growing in the form of close encrustations on seaweeds, this species may take on entirely different habits of growth. The zooecia are now dissociated, growing in single lines over the substratum; now forming erect tufts, composed of single lines of zooecia or of several rows. The erect, branching habit appears to be induced in the first instance by the character of the seaweed on which the colony begins life. Thus colonies which encrust the thin branches of Corallina may have impressed on them something of the mode of growth of the seaweed, so that when they extend beyond the tips of the branches of the Corallina, they continue to grow in delicate branches, which still retain more or less the same diameter as those which form their base. An extreme variation results in the beautiful form known as Electra verticillata, in which the zooecia are arranged with great regularity in whorls, which together form erect branches.[^[586]] But with all these variations, the zooecia are so much alike that it is hardly possible to regard the extreme forms as more than varieties of a single species. A careful examination of this case would convince most observers that the characters of the zooecium are a more trustworthy guide to classification than those of the entire colony, a result which was first clearly stated by Smitt, and amply confirmed by Hincks.[^[587]]

The avicularia of the Cheilostomata afford useful help in classifying this group; but while certain genera are always provided with avicularia, others include some species with these organs, and other species without them. Again, while the species of some genera (e.g. Cellepora) possess a great variety of forms of avicularia, the same pattern of avicularium may characterise several widely different genera. Further, the position of the avicularium may be very different in species which are apparently closely related. Well-developed vibracula, although constant in their occurrence in such forms as Scrupocellaria (Fig. 254) and Caberea (Fig. 242), occur here and there in species of encrusting forms which are ordinarily placed in very different families.

Now although some of these discrepancies are perhaps due to errors in classification, whereby species which are really allied have been wrongly placed in distinct genera, this explanation would not prove satisfactory in all cases. Thus in Bugula, a genus which is specially characterised by the high development of its avicularia, these organs are normally absent in B. neritina. The fact that this species was rightly placed in the genus has been confirmed by the discovery made by Waters[^[588]] that avicularia occur in specimens which are believed to be identical with that species.

Fig. 254.—A, Front view, and B, back view of part of a branch of Scrupocellaria scabra, Van Ben., Durham Coast, × 43; a, lateral avicularium; a', smaller median avicularium; ap, membranous aperture; f, fornix; r, rootlet; s, seta of vibraculum; v.z, vibracular zooecium.

1. The Cyclostomata appear to fall naturally into two main groups, (A) the Articulata, including the Crisiidae (Fig. 237), distinguished by their erect branches, divided at intervals by chitinous joints; and (B) the Inarticulata, which include the remaining families, whether erect or encrusting, agreeing in the negative character of being unjointed.

2. The Cheilostomata consist of (A) the Cellularina, including the flexible, erect forms, such as Bugula (Fig. 233) and Scrupocellaria (Fig. 254); (B) the Flustrina, to which belong Flustra (Fig. 232), Membranipora (Fig. 256, A, B), Micropora (Fig. 256, C), and other forms in which the front wall of the zooecium is either membranous, or depressed and marked off by a ridge-like margin; (C) the Escharina, including the great majority of forms, in which no part of the front wall remains membranous, the wall of the zooecium being wholly calcified.

3. The Ctenostomata comprise (A) the Alcyonellea or encrusting forms; and (B) the Vesicularina or branching forms. The zooecia in the latter subdivision (Fig. 238) are given off from a tubular stem or stolon, which is usually erect and branching.

We thus have the following arrangement of recent forms. The genera mentioned are for the most part those which have already been alluded to in the preceding account:—

Sub-class I. Entoprocta.

Loxosoma, Pedicellina, Urnatella.

Sub-class II. Ectoprocta.

Order 1. Gymnolaemata.

Sub-order 1. Cyclostomata.

A. Articulata. Crisia.

B. Inarticulata. Hornera, Idmonea, Tubulipora, Stomatopora,

Diastopora, Entalophora, Lichenopora.

Sub-order 2. Cheilostomata.

A. Cellularina. Aetea, Eucratea,[^[589]] Catenicella,

Cellularia, Gemellaria, Menipea, Scrupocellaria,

Caberea, Notamia (= Epistomia), Bicellaria, Bugula,

Beania.

B. Flustrina. Cellaria, Flustra, Membranipora, Electra,

Lunulites, Membraniporella, Cribrilina, Micropora,

Selenaria.

C. Escharina. Retepora, Microporella, Lepralia, Porella,

Smittia, Mucronella, Schizoporella, Schizotheca,

Mastigophora, Porina, Cellepora.

Sub-order 3. Ctenostomata.

A. Alcyonellea. Alcyonidium, Flustrella.

B. Vesicularina. Vesicularia, Amathia, Bowerbankia,

Farrella, Hypophorella, Triticella, Mimosella,

Victorella, Paludicella.

Order 2. Phylactolaemata.

Fredericella, Plumatella (including Alcyonella), Lophopus,

Cristatella, Pectinatella.

Even this classification, which deals only with the larger groups, must not be made use of without a word of warning. The division of the Cheilostomata is a matter of great difficulty; and no scheme which has yet been suggested can be regarded as more than tentative. The great number of forms included in this group makes its subdivision extremely desirable from the point of view of convenience; but a further knowledge of the anatomy and of the development of many of the forms of doubtful systematic position is probably necessary before any scheme which is likely to be permanent is put forward. Those who desire to make a further study of the classification of the Polyzoa should refer to the works of Hincks,[^[590]] Busk,[^[591]] MacGillivray,[^[592]] and Gregory.[^[593]]

The Polyzoa do not appear to lend any valuable assistance towards settling the disputed problems of Geographical Distribution. They are not in any case terrestrial, while the fresh-water species do not always respect the limits between the great zoogeographical regions. It has already been pointed out (p. [504]) that Plumatella, Fredericella, and Lophopus are believed to occur in Australia, and the first-named genus is practically world-wide in its distribution.

Many marine forms also have a surprisingly wide distribution. Thus among the British species which are described by Mr. Hincks as occurring from Norway to New Zealand are Membranipora pilosa, Scrupocellaria scruposa, Cellaria fistulosa, Microporella ciliata, and M. malusii. Even if it should be proved that specific differences do exist between the southern forms and our own, there can be no doubt of the wide distribution of certain species. It was pointed out by D'Orbigny that Bugula neritina has the habit of attaching itself to the bottoms of ships, a fact which may possibly account for the wide distribution of this species; although it would not be safe to assume this explanation of the facts in all cases. Other Polyzoa, on the contrary, have a more restricted range. Thus Catenicella is specially characteristic of the Australian region.

It is perhaps surprising that marine Polyzoa should in so many cases have so wide a range. Even though it is the rule for Polyzoa to have free larvae, the period during which these larvae are free-swimming is, so far as is known, a short one in most cases. Cyphonautes is a common pelagic form (see p. [510]), and probably remains for a considerable period in the larval condition. Other Polyzoon-larvae appear to fix themselves very soon after their birth; and this would not appear to give much time for them to be carried to great distances by ocean-currents. It may, however, be suggested that it does not follow that because we know that a larva may, under favourable conditions fix itself a few minutes after it becomes free, we should be justified in assuming that that larva would not retain for a long period the power of undergoing a normal metamorphosis should it be drifted away from suitable fixing-grounds.

Palaeontology.[^[594]]—The number of fossil Polyzoa is enormous. D'Orbigny devoted two hundred plates and more than a thousand octavo pages[^[595]] to a Monograph on the Cretaceous Polyzoa of France. Many of the fossil forms are extraordinarily well preserved, and there is often no difficulty in recognising the identity between certain fossil species belonging to the more recent formations and living forms. It thus becomes necessary to consult Palaeontological memoirs in working at recent Polyzoa.

While the great majority of fossil Polyzoa do not differ in any essential particular from recent species, this is not altogether the case with the Palaeozoic forms. Leaving out of account the Stromatoporoids, which have been variously referred to the Sponges, Hydrozoa, and Foraminifera, as well as to the Polyzoa, the Palaeozoic strata contain large numbers of peculiar Cyclostomata, together with members of the Trepostomata, a fourth Sub-order of Gymnolaemata, allied to the Cyclostomata. The Trepostomata are for the most part Palaeozoic, but a few survived as late as the Jurassic period.[^[596]] These, with the other Polyzoa from the same formations, are considered by Dr. Gregory in his recently published Catalogue of the Fossil Bryozoa in the British Museum (1896).

The number of Polyzoa recorded from the earlier secondary strata is small. The majority of the known Jurassic forms belong to the Cyclostomata; and one or two Cheilostomes are recorded from the same period. Recent papers by Walford[^[597]] on Jurassic Polyzoa contain the description of genera which are believed to be intermediate between the Cyclostomata and Cheilostomata, particularly with regard to the characters of their ovicells. Although it is not impossible there may be a connection between the ovicells of these two groups, it has yet to be proved that the two sets of structures are homologous.

The Cretaceous period marks the commencement of a large number of Cheilostome genera, although the Cyclostomes still remain numerous.

In the Tertiary formations the Cyclostomes gradually become less numerous, and although in earlier geological periods they far outnumbered the Cheilostomes, these relations are now reversed. Certain Tertiary strata, and particularly the Coralline Crag (Pliocene), are remarkable for the extremely large number of Polyzoa they contain. It will be noticed that no mention has been made of the Entoprocta, the Ctenostomata, and the Phylactolaemata. Their absence in the fossil condition[^[598]] need not, however, be a matter for surprise, as none of these forms are so well suited for being fossilised as are the calcareous Cyclostomata and Cheilostomata. There is consequently no adequate reason for assuming that the absence of a palaeontological record implies that these groups have been recently evolved.

Determination of Genera of Marine Polyzoa.—The species to which a Polyzoon belongs can only be determined, in most cases, with the assistance of the low powers of a microscope. There are very great advantages in the use of a binocular instrument, by means of which a microscopic preparation appears with its parts standing up in proper relief.

In the case of the calcareous forms, the external characters may be more readily made out in a dry preparation than in any other way. For this purpose, the colony should be washed with fresh water, in order to remove the salts, which otherwise crystallise out on drying and obscure the surface. Preparations of this kind must be looked at with the aid of reflected light. Canada-balsam or glycerine preparations are also valuable, whether stained or unstained; and are essential for the examination of the softer forms. In the case of erect species, both surfaces of the branch should be looked at. The opercula, avicularia, and rosette-plates afford important systematic characters in the case of the Cheilostomata.

It must not be forgotten to take account of the condition of the zooecia at different ages. The old zooecia often become entirely altered in form, by the deposition of additional calcareous matter, or by the loss of certain parts present in the younger zooecia. Thus the marginal spines may be entirely lost in the older individuals, while in those forms which develop a "peristome" (see Fig. 255 and p. [524]), the characters of the orifice can often be determined in the young zooecia only. It is thus essential to examine the growing ends of the branches or the rim of the colony, as the case may be.

Fig. 255.—Illustrating the nature of a secondary orifice (Cheilostomata). A, Mucronella coccinea Abildg., Scilly Is., × 40. The ovicell (o) overhangs the primary orifice, which is concealed by the great development of the peristome, produced into the mucro (mu); t, the three teeth (denticles) within the secondary orifice; a, avicularium. B, Porella compressa Sowb., Norway, × 40; p.o. primary orifice, above which is a concave lamina, the beginning of the ovicell. In the lower zooecium the ovicell (o) is further grown. The primary orifice is still visible, but it is partially concealed by the growth of the peristome, which encloses a minute avicularium; m, mandible of avicularium. C, Older part of the same colony; pr, peristome; s.o, secondary orifice; o', adult ovicell; p, pores.

In order to make preparations with the tentacles expanded, hydrochlorate of cocaine, chloral hydrate or spirit should be added gradually to the water. When the animals are completely anaesthetised they may be killed by means of a 7-10 p.c. solution of sulphate of copper (best made in distilled water or in rain water). This method gives admirable results in the case of both fresh-water and marine Polyzoa. The use of formaline (see p. [229]) may be strongly recommended for the Vesicularina.

The only recent work dealing with all the marine British forms is Mr. Hincks' invaluable History of the British Marine Polyzoa.[^[599]] As the use of this book, unaided by any artificial help, is by no means easy to the beginner, the following key has been compiled as an index to the genera. The Entoproct forms, Loxosoma and Pedicellina (see pp. [488-491]), are not included in the table.

Fig. 256.—Illustrating the terminology of the front surface of the zooecium (Cheilostomata). A, Membranipora (Electra) pilosa L., Cromer, × 47; ap, the membranous "aperture;" o, orifice. B, Membranipora flemingii Busk, Plymouth, × 60; ap, the aperture, enclosed in a calcareous "area" (a); av, avicularium; s, marginal spines. C, Micropora coriacea Esper, Plymouth, × 43; a, area (calcareous); o, operculum; ov, ovicell.

In order to facilitate the use of the table here given in conjunction with Mr. Hincks' work, the nomenclature there adopted has been followed throughout. References to other descriptions of the species may be obtained by consulting Miss Jelly's admirable Synonymic Catalogue of the Recent Marine Bryozoa.[^[600]]

Terminology.—A few technical terms must of necessity be employed. The colony is adherent when its zooecia are attached to the object on which the colony is growing. The zooecium is the body-wall of a single individual; and, except in transparent species, is the only part which can be seen from the outside in the retracted condition of the polypide or tentacles with the alimentary canal. The outermost layer of the zooecium is known as the ectocyst; it may be simply membranous, or calcified, or may be rendered opaque by foreign bodies; its surface in calcareous forms is often marked by pores (Fig. 239, C, p), which are vacuities in the calcareous wall, closed externally by membrane. A special median pore (Fig. 241, A, m.p) may occur, and is in some cases at least a complete perforation through the body-wall.

The tentacles are protruded through the orifice, which in Cheilostomata is usually guarded by a movable chitinous lid, or operculum (Fig. 256, A, o). Should the ectocyst be thickened or raised into a ridge surrounding the orifice, a tubular passage results, known as the secondary orifice (Fig. 255), at the deeper end of which is the true orifice. The peristome (Fig. 255, C, pr) is the raised or thickened part which gives rise to the secondary orifice. Should the zooecium be outlined by a raised ridge, the part so enclosed is known as the area (Fig. 256, C, a), if calcareous. The aperture or opesia (Fig. 256, A, B, ap) is a membranous part of the front surface; and may consist of the whole or part of the area. The orifice or the aperture is commonly provided with spines (Fig. 256, B, s).

Fig. 257.—A, Cribrilina annulata Fabr., Norway, × 33; c, calcareous bars concealing the membranous aperture: B, Membraniporella nitida Johnst., Plymouth, × 45; a, calcareous bars growing up round the margin of the aperture; b, the same, further developed; c, the same, completely formed (as in A); av, avicularium; o, immature, and o', mature, ovicell; s, marginal spines.

The avicularium and the vibraculum are specially modified zooecia (see p. [482]), which occur in a great variety of forms, in certain Cheilostomata only. The operculum of the ordinary zooecium is represented by the mandible (Fig. 239, B, m) in the avicularium, and by the seta (Fig. 242, s) in the vibraculum. The representative of the zooecium itself is known as the avicularian (Fig. 239, A, a.z) or vibracular zooecium (Fig. 242, v.z).

An ovicell is a swelling in which the embryo develops, in certain Cyclostomata (Fig. 237) and Cheilostomata (Fig. 241, A, o). A stolon (Fig. 238, B, st) is a stem, not formed of fused zooecia, from which new individuals originate. An internode, in a jointed colony, is the part between any two joints. The fornix or scutum (Fig. 254, A, f) is a modified spine which in some Cheilostomata overhangs the aperture. A mucro (Fig. 255, A, mu) is a spike or protuberance developed just below the orifice. A sinus (Fig. 239, B, s) is a slight bay on the lower margin of the orifice.

The orifice opens at the upper end of the zooecium, on its front surface. The length of the zooecium is the distance from the upper to the lower ends, and the width the distance between its sides.

1.		One or more of the following characters: orifice provided with an operculum; avicularia or vibracula present; a globular ovicell above the orifice of certain zooecia (Cheilostomata) [7]
		Opercula, avicularia, vibracula, and ovicells completely absent, or inconspicuous. Calcareous or non-calcareous. If calcareous, the orifice is not at the end of a free cylindrical portion [3]
		Calcareous; zooecia cylindrical, often united for the greater part of their length, but usually ending in a free cylindrical portion, which bears the terminal orifice. The zooecia may be much obscured by calcifications surrounding their basal parts [2]
2.		Zooecia long, tubular, with a lateral membranous region at the upper end, given off quite separately from a creeping stolon Aetea
		Zooecia more or less united to one another, orifice without chitinous operculum (Cyclostomata[[601]]) [63]
3.		Zooecia without marginal spines; arising from a branching axis, which is not formed of zooecia [74]
		Colony adherent; or erect, fleshy and slightly branched; or erect, encrusted with earthy matter and repeatedly branched [72]
		Characters not as above [4]
4.		Zooecia minute, boat-shaped, united by a delicate tube. Aperture large, with marginal spines Beania mirabilis
		Colony delicate, erect; zooecia wider above than below [5]
5.		No marginal spines [6]
		Zooecia uniserial; with marginal spines. Branches arising from the top of a zooecium Brettia
6.		Zooecia uniserial; branches arising just below the large aperture. An ovicell may be developed above the orifice of a modified zooecium Eucratea chelata
		Zooecia somewhat pear-shaped; orifice small, semicircular Huxleya fragilis
7.		Colony erect [8]
		Zooecia in several layers forming confused masses [30]
		Colony entirely adherent,[[602]] the zooecia usually in a single layer [31]

Erect Cheilostomata.

8.		Branches cylindrical, calcareous, divided by chitinous joints. Orifices arranged all round the branch Cellaria (Fig. 239, A)
		Branches flexible, jointed or unjointed. Orifices not arranged all round the branch. [9]
		Calcareous, unjointed, rigid [21]
9.		Branches leaf-like, flattened [10]
		Branches not leaf-like [11]
10.		Avicularia resembling birds' heads, movable Bugula (Fig. 233)
		Avicularia not resembling birds' heads, unstalked; or absent. Colony broadly leaf-shaped, composed of a single layer or of two layers of zooecia Flustra (Fig. 232)
11.		Zooecia in pairs, at the same level [12]
		Zooecia not obviously paired [13]
12.		Branches numerous, straight. Zooecia back to back, with an oblique aperture. No avicularia Gemellaria loricata
		Branches delicate, curved. A pair of stalked avicularia between each two pairs of zooecia Notamia (= Epistomia) bursaria
13.		Avicularia or vibracula conspicuous [14]
		Avicularia or vibracula inconspicuous or absent [17]
14.		Avicularia resembling birds' heads, movable. Vibracula absent [15]
		Avicularia large, unstalked. Vibracula present or absent [16]
		Avicularia inconspicuous. Setae of the vibracula large, very conspicuous, on oblique vibracular zooecia, which almost cover the backs of the branches Caberea (Fig. 242)
15.		Zooecia in two series, alternate, with one or several conspicuously long marginal spines Bicellaria
		Zooecia in two or more series. Aperture occupying most of the front of the zooecium. Colony often spiral. Avicularia usually large Bugula (Fig. 233)
16.		Zooecia long, narrow below, commonly in triplets, with two lateral avicularia to each triplet. Fornix present. Menipea ternata
		Zooecia biserial, a considerable number forming an internode separated by a joint (often inconspicuous) from the next internode. Lateral avicularia usually large. Vibracular zooecia on the back or sides of the branches Scrupocellaria (Fig. 254)
17.		Characters as in Scrupocellaria (No. 16), but with inconspicuous avicularia. A branched fornix Scrupocellaria reptans
		Vibracula absent [18]
18.		A single, short, marginal spine; or none [19]
		Marginal spines present [20]
19.		Characters as in No. 6 Eucratea chelata, Huxleya fragilis
		Zooecia biserial. Aperture large, the semicircular orifice at its upper end, where there is commonly a short spine Cellularia peachii
		Zooecia in one or two series. Branches originating from the backs of the zooecia, and facing in the opposite direction to the parent branch. Aperture small Scruparia clavata
20.		One or more conspicuously long marginal spines. Avicularia present or absent Bicellaria
		Zooecia uniserial (see No. 5) Brettia
		Zooecia biserial, in short internodes. An inconspicuous avicularium below the aperture. Fornix present Menipea jeffreysii
21.		Colony consisting of a network of narrow branches, the zooecia opening only on one of their surfaces Retepora
		Colony large, brittle, composed of contorted plates, uniting irregularly, usually composed of two layers of zooecia. Orifice large, indented laterally Lepralia foliacea
		Branches delicate, cylindrical [22]
		Branches or lobes coarser, not necessarily cylindrical [24]
22.		Branches composed of four rows of zooecia [23]
		Zooecia in more than four regular, longitudinal rows. Peristome raised, and, with the ovicell, forming a swelling on the surface of the branch Escharoides quincuncialis
23.		Orifice circular. A row of pores round the margin of the zooecium. A median pore resembling a small orifice below the true orifice. Small lateral avicularia Porina borealis
		Orifice surrounded by a peristome, produced into a mucro beneath the orifice. No pores Palmicellaria elegans
24.		Zooecia arranged in regular series [25]
		Zooecia irregularly heaped, their long axes often perpendicular to the surface of the colony. Mucro largely developed, concealing the form of the orifice, and bearing an avicularium Cellepora
25.		Orifice with a sinus; or peristome interrupted or extended below into a sinus-like outgrowth, which usually includes a small avicularium [26]
		Neither median sinus nor interrupted or extended peristome [28]
26.		Orifice with a sinus Schizoporella (Fig. 239, B)
		Peristome interrupted or extended below [27]
27.		Branches of various forms. Surface of the older parts very even. Secondary orifice rather long, usually wider above, enclosing a small avicularium below, and appearing as a hole in the even surface of the branch Porella (Fig. 255, B, C)
		A prominent tooth projects into the orifice from its lower side. Zooecia with thin walls Smittia landsborovii (Fig. 239, C)
		No tooth in the orifice, at the side of which is a small avicularium. Old zooecia with thick walls. Colony composed of a short stem and flattened branches Escharoides rosacea
28.		A tooth projects from the lower side into the large, subcircular orifice, on each side of which is a small oval avicularium (colony erect or encrusting) Mucronella pavonella
		No tooth: mucro sometimes present [29]
29.		Branches cylindrical. Old zooecia with thick walls. Orifice in young zooecia longer than broad; beneath it a median pore, and in some cases a lateral avicularium with vibraculoid mandible Diporula verrucosa
		A distinct mucro, which may bear an avicularium above Palmicellaria

Encrusting Cheilostomata.

30.		Usually growing on a small univalve shell. Orifice longer than broad, indented laterally. Mucro present Lepralia edax
		One or two conspicuous processes, each bearing an avicularium, near the orifice, which is often concealed. Avicularia in many cases found on other parts of the colony Cellepora
31.		Zooecia distant; or in single rows [32]
		Zooecia forming continuous expansions [36]
32.		An oval aperture, larger than the orifice [33]
		No aperture [34]
33.		A tubular process below the aperture, in some cases: zooecia very narrow below Eucratea chelata, var. repens
		No tubular process below the aperture Membranipora
34.		Peristome much raised below, collar-like Phylactella
		Peristome not much raised below [35]
35.		Zooecia minute, much narrowed below. Orifice small, usually with a sinus Hippothoa
		Zooecia not narrowed below. Orifice with a sinus Schizoporella
36.		Zooecia partly separated by a thin calcareous crust. Colonies small [37]
		Zooecia contiguous [38]
37.		Zooecia pear-shaped. Orifice with a sinus Hippothoa expansa
		Zooecia ovoid. Orifice subcircular, with a tubular peristome Lagenipora socialis
38.		Orifice close to the upper end of the zooecium (unless crowned by an ovicell). Front of the zooecium marked by transverse or radiating furrows or lines. The very young zooecium may possess a membranous area, which becomes roofed in by the union of two lateral series of converging bars (Fig. 257) [39]
		Characters not as above [40]
39.		Furrows with uniserial rows of pores (often minute), which are rarely irregular Cribrilina (Fig. 257, A)
		No rows of pores. Distinct transverse lines or spaces and a median longitudinal suture between the bars Membraniporella (Fig. 257, B)
40.		Zooecia arranged in regular series [41]
		Zooecia irregularly[[603]] heaped together (cf. No. 30) Cellepora
41.		Primary orifice conspicuous; with a sinus, or with a peristome extended or interrupted below, and sometimes simulating a sinus [42]
		Neither sinus[[604]] nor interrupted peristome [44]
		Surface of the old zooecia much thickened, so that the secondary orifice does not project beyond the most prominent parts of the zooecium. Secondary orifice concealing the primary orifice, wider above, enclosing a small avicularium below Porella (Fig. 255, B, C)
42.		Primary orifice with a sinus, but no tooth [43]
		A prominent tooth projects into the orifice from its lower side. Peristome interrupted or with a sinus. Surface of the old zooecia not much thickened Smittia
43.		Orifice with a sinus and long spines. Peristome interrupted. Ovicell with a wedge-shaped or linear longitudinal fissure. Avicularia generally present, the avicularian zooecium conspicuous. Schizotheca
		Orifice semicircular. Vibracula present, near the orifice. Mastigophora (Fig. 241, B)
		Orifice semicircular or subcircular. No vibracula; avicularia with vibraculoid mandibles may occur Schizoporella (Fig. 239, B)
44.		Zooecium with a median pore; or completely tubular above [45]
		Zooecium with no median pore. The orifice may be partially surrounded by a collar-like development of the peristome, but it is not completely tubular [49]
45.		Orifice not tubular. A median pore Microporella (Fig. 241, A)
		Orifice tubular [46]
46.		Zooecia narrow or small [47]
		Zooecia ovoid [48]
47.		Orifice markedly tubular. Median pore conspicuous Porina tubulosa
		Colony very small. Zooecia irregularly arranged, with no median pore Celleporella
48.		Zooecia very convex, with a granular surface; ovicells set far back. Orifice wider than long Mucronella microstoma
		Young zooecia with stellate pores. A minute avicularium, or merely a pore, on the upper and lower sides of the orifice in some zooecia. Anarthropora monodon
49.		Front of zooecium with an elevated margin, enclosing an area [50]
		Area not present [55]
50.		Front wall wholly calcareous [51]
		Front wall wholly or partly membranous [54]
51.		Avicularian or vibracular zooecia replacing an ordinary zooecium, or at least situated between the zooecia [52]
		Avicularia and vibracula absent, or if present not replacing a zooecium [53]
52.		Vibracula present. Colonies small. A pair of longitudinal slits within the area Setosella vulnerata
		Very large avicularia present. Ovicell closed by a movable lid. Orifice subcircular, with a minute lateral tooth on each side. Thalamoporella[[605]] (Steganoporella) smittii
53.		Orifice semicircular, quite at the upper end of the zooecium; usually with a knob on each side Micropora coriacea[[606]] (Fig. 256, C)
		A transverse chitinous plate lies immediately below the operculum. A vibraculoid spine may occur Megapora ringens
54.		Area entirely membranous, usually bordered by spines. Membranipora (including Electra[[607]]) (Fig. 256, A)
		Membranous portion reduced to a small portion, which may be variously lobed, enclosing the orifice. Membranipora (other species) (Fig. 256, B)
55.		Peristome present. No mucro [56]
		Peristome absent; or if present, with a mucro [57]
		See also Mucronella pavonella, No. [28]).
56.		Peristome collar-like, much raised below and at the sides of the orifice, deficient above. No avicularia Phylactella
		Orifice large, longer than broad. Peristome not deficient above the orifice Lepralia
57.		Wall of zooecium thin, shiny, and without pores [58]
		Not agreeing with the characters given under No. 58 [59]
58.		A minute avicularium above the orifice, or where an ovicell is present, situated at the summit of that structure. Zooecia not quite contiguous. Mucro sometimes present. Chorizopora brongniartii
		No avicularia. Ovicells on rudimentary zooecia, lying in a plane superficial to that of the rest of the colony. Zooecia long. Schizoporella hyalina
59.		A more or less distinct mucro or prominence beneath the orifice. [60]
		Mucro rarely present. Orifice nearly always longer than broad, or nearly circular, usually large, and slightly indented laterally. Lepralia
60.		A tooth projects into the orifice from its lower side [61]
		No tooth [62]
61.		Colony glistening. Orifice much obscured by the mucro and by stout spines developed from the peristome. Tooth (concealed in old zooecia) large, strongly curved to one side. Rhynchopora (Rhynchozoon[[608]]) bispinosa
		Tooth of the lower margin of the orifice symmetrical, sometimes bifid. Avicularia may be present laterally, but are not developed on the mucro Mucronella (Fig. 255, A)
62.		Orifice at least half the width of the zooecium, bordered below by a well-developed prominence or "umbo." Surface of the zooecium strongly areolated round the margin Umbonula[[609]]
		Orifice considerably less than half the width of the zooecium. Schizoporella (Fig. 239, B)

Encrusting Cyclostomata.

63.		Colony erect. Branches of two or one series of zooecia, divided at intervals by chitinous joints. Ovicells pear-shaped. Crisia (Fig. 237)
		Colony erect, unjointed [69]
		Colony in the main adherent; or circular; or lobed [64]
64.		Colony more or less circular, discoidal or cup-shaped, sometimes forming secondary colonies by marginal budding [65]
		Colonies not circular [68]
65.		Zooecia separated by calcified interspaces, which may contain large pores, often difficult to distinguish from the orifices [66]
		No large pores as above. Orifices not spiny. Zooecia nearly always contiguous, except where an ovicell is developed [67]
66.		Colony composed of one or more convex discs, bearing radial ridges, each composed of many zooecia Domopora
		Colony encircled by a thin calcareous lamina, which gives rise to new zooecia, its centre usually devoid of zooecia when adult, and often bearing the orifice(s) of the ovicell. Zooecial orifices often spiny. Lichenopora
67.		Zooecia with a long, tubular, free portion, in some cases curved in a horizontal plane. Colony fan-shaped until a late stage. Tubulipora flabellaris
		Tubular portion absent, or for the most part curved in a vertical plane. Some of the orifices may be closed by a calcareous plate. Colony circular or bluntly lobed Diastopora
68.		Zooecia in one or few series, forming a linear or branched colony, which is closely adherent, but may give rise to short erect portions. Branches narrow, but often broadening at their ends. Zooecia usually with a free upper end Stomatopora
		Colony broadly lobed, some of the zooecia in transverse or oblique ridges composed of contiguous zooecia, arranged like a row of organ-pipes Idmonea serpens
		Colony broadly lobed, or fan-shaped; zooecia in many series, which are not arranged like organ-pipes Tubulipora
69.		Well branched. Orifices confined to one surface of the colony [70]
		Not much branched [71]
70.		Zooecia in transverse rows, their upper ends united in the manner of a row of organ-pipes. Ovicell (when present) an inflation of the front of the branch Idmonea atlantica
		Zooecia not in regular transverse rows. Ovicell (when present) large, mostly on the back of the branch Hornera
71.		Branches cylindrical, their ends massive and raised into radial ridges, which carry the orifices Domopora stellata
		Ends of zooecia tubular, arranged all round the branch. Entalophora

Encrusting Ctenostomata.

72.		Colony entirely adherent, or forming thick, soft, erect lobes [73]
		Colony erect, well-branched, dark and opaque, resembling seaweed. Zooecia with a long tubular free portion Anguinella palmata
73.		Orifice large, with two distinct lips. A variable number of stout, brown spines. Encrusting Flustrella hispida
		Orifice small, rounded, borne by a more or less distinct papilla. Encrusting or erect. Zooecia crowded, rarely in single lines. Alcyonidium
		Orifice small, rounded. Zooecia widely separated, connected by narrow tubes Arachnidium
74.		Axis of colony erect, usually branched [75]
		Axis creeping [79]
75.		Zooecia in elongated clusters, which occur at intervals [76]
		Zooecia not grouped; or in irregular groups; or in whorls [78]
76.		Zooecia regularly biserial [77]
		Zooecia long, less regularly arranged. Polypide with a gizzard. Bowerbankia (Fig. 238)
77.		Clusters of zooecia very regular, occurring immediately below a bifurcation of the axis. Zooecium with a broad base, not movable. Amathia lendigera
		Zooecia arranged like the pinnules of a leaf, with a constricted base, and movable on the branch Mimosella gracilis
78.		Main stem zigzag. Branchlets delicate, many ending in sharp points. Zooecia small, ovoid Vesicularia spinosa
		Axis jointed. Zooecia small, in small clusters. Polypide without a gizzard Valkeria uva, var. cuscuta
		Zooecia in whorls, attached to the axis by thread-like stalks, much longer than themselves Hippuraria egertoni
79.		Zooecia pear-shaped, produced at the lower end into a distinct stalk. Gizzard absent [80]
		Zooecia not distinctly stalked, although sometimes constricted at the base [81]
80.		Stalk long. Zooecium movable on its stalk, compressed, with a membranous area on one side. Twelve or more tentacles. Usually found on Crustacea Triticella
		Stalk variable. Zooecium very transparent; orifice bilabiate. Ten to sixteen tentacles Farrella repens
		Zooecium very small, much elongated and narrow. Eight tentacles. Valkeria tremula
		(See also Arachnidium, No. 73).
81.		Zooecia short, minute, with a few short spines on each side of its broadened base. Upper end tubular Buskia nitens
		Zooecia elongated [82]
82.		Zooecia transparent [84]
		Zooecia brown, often quite opaque [83]
83.		Zooecia large (about 1⁄16 inch long), distant, constricted at the base, bearing scattered bristles. Usually found on Crabs or Hydroids. Avenella fusca
		Zooecia tall, cylindrical, not constricted at the base. Cylindroecium
84.		Zooecia minute. Axis dilating at intervals into swellings, from which new zooecia originate. These may give rise to new stolons, or directly to new zooecia. No gizzard. Found in brackish or fresh water Victorella pavida
		Axis not dilated, as above [85]
85.		Zooecia small, in small groups. No gizzard Valkeria uva
		Zooecia long, scattered or in groups. Gizzard present. Bowerbankia (creeping forms)

It is highly probable that the Ctenostome genus Hypophorella[^[610]] will before long be added to the British Fauna. The animal consists of delicate stolons, which give off small zooecia at intervals; and it is known to excavate passages in the substance of the tubes of certain Polychaet worms (Chaetopterus and Lanice).

ADDENDUM TO CHAETOGNATHA

Since the Chapter on the Chaetognatha was printed the following list[^[611]] of "The Known Chaetognaths of American Waters" has appeared:—

1. Sagitta elegans Verr. This species resembles S. bipunctata (vide pp. [191] and [193]), but differs in size, in the relative proportions of caudal and body segments, and in the presence of diverticula from the intestine.

2. Sagitta flaccida Con. This species resembles S. hexaptera (vide p. [193]); it is, however, smaller (length, 1.3-1.8 cm.) and has more spines (anterior, 7-8, posterior, 10-12), and its tail segment is relatively smaller.

3. Sagitta tenuis Con. Length, 5.25 mm.; hooks, 7-8; anterior spines, 4-5; posterior spines, 7-10.

4. Sagitta hispida[^[612]] Con. Length, 7-11 mm.; hooks, 8-9; anterior spines, 4-5; posterior spines, 8-15; tail segment one-third body length; intestine with two diverticula; sensory hairs very numerous.

5. Sagitta hexaptera (vide p. [193]).

6. Krohnia hamata (vide p. [194]).

7. Spadella maxima Con. Length, 5.2 cm.; hooks, 6; anterior spines, 3-5; posterior spines, 5-7; epidermal thickenings round the neck.

8. Spadella draco (vide p. [194]).

9. Spadella schizoptera[^[612]] Con. An opaque, yellowish-brown species living among algae. Length, 4 mm.; hooks, 8; anterior spines, 4-6; posterior spines wanting. Caudal segment occupies one-half the body length.

Professor Verrill states that the name S. gracilis (vide p. [191]) was due to a clerical error, the species really referred to being S. elegans.

A. E. S.

CHAPTER INDEX

Every reference is to the page: words in italics are names of genera or species; figures in italics indicate that the reference relates to systematic position; figures in thick type refer to an illustration; f. = and in following page or pages; n. = note.

Acanella, as host, [298]

Acanthobdella, [395]

Acanthocephala, [123], [124], [174] f.;

embryology, [179];

classification, [181]

Acanthocotyle, [73]

Acanthodrilidae, [357], [362], [381], [383], [384]

Acanthodrilus, [356], [363], [366], [372], [382], [384];

chaetae, [350]

Acanthozoon, [20]

Accessory gut, of Polychaeta, [305]

Aceros, [19]

Achaeta, [445]

Acholoe, [297]

Aciculum, [247]; fossil, [302]

Acmostoma, [50]

Acoela, [42];

occurrence and habits, [43];

reproduction, [47];

classification, [49]

Acotylea, [16] f., [17], [18]

Acrorhynchus, [49];

occurrence, [44]

Actinotrocha larva, [458]

Actinurus, [201], [222]

Acyclus, [221]

Adaptation, of Trematodes, [52], [62];

of Cestodes, [74];

of Nematodes, [161]

Adherent, [523]

Adineta, [204], [222], [227]

Adventitious avicularia, [482]

Aeolosoma, [349], [353], [354], [360], [370], [374], [375]

Aetea, [518], [525]

Agassiz, on Syllidae, [280]

Alaurina claparedii, [49]

Albertia, [204], [210], [213], [224], [227]

Alciope, [315]

Alciopids (Alciopina), [314];

head, [263];

parapodium, [265];

habit, [291];

light-organs, [294]

Alciopina parasitica, [298]

Alcyonella, [494], [505], [518]

Alcyonellea, [518]

Alcyonidium, [477], [480], [492], [518], [532];

structure of zooecium, [469];

reproduction, [507], [508];

larva, [510], [511]

Alimentary canal—see Digestive System

Alitta, [317]

Allantonema, [131], [150], [151], [161]

Allman, on Polyzoa, [474], [475]

Alloeocoela, [43]; habits, [46];

reproduction, [47];

classification, [50]

Alloiogenesis, [66] n.

Allolobophora, [351], [367], [369], [371], [386], [389], [390] f.;

cocoons, [365]

Allostoma pallidum, [50]

Alluroides, [379]

Allurus, [351], [366], [370], [389];

cocoons, [365]

Alma, [352] f., [387]

Alternation of generations, [66], [81], [281]

Amathia, [481], [518], [532]

Ammocharidae, [258], [325]

Ammotrypane, [273], [331];

intestine, [271]

Ampharete, [330]

Ampharetidae, [258], [330]

Amphibia, Trematodes of, [55], [62], [71], [72];

Nematodes of, [163]

Amphichaeta, [377]

Amphicoerus, [49]

Amphicora, [339]

Amphicorine, gill, [261]

Amphicorinidae, [258], [339]

Amphicteis, [330]

Amphictenidae, [258], [330]

Amphiglena, [273], [339]

Amphileptus, [235]

Amphilina, [91]

Amphinome, eye of, [255];

A. smaragdina, colour, [293]

Amphinomidae, [258], [318];

shape, [259];

caruncle, [260], [273] n.;

head, [262], [263];

parapodium, [264];

cirri, [265];

chaetae, [267], [267];

in Lepas, [297]

Amphiporus, [102], [114];

British species, [110]

Amphiptyches, [77]

Amphistomatidae, [73]

Amphistomum, [71], [73];

A. hominis, [63]

Amphitrite, [327], [328];

gill, [329]

Ampullaria, Temnocephala with, [53]

Anachaeta, [350], [376], [395]

Anal, cirri, [259];

funnel, [259], [332], [333];

vesicles, [358], [436]

Anangian worms, [253]

Anarthropora, [529]

Ancylostomum, [143], [163]

Andrews, on Sipunculus, [417], [426]

Angiostomum, [134]

Angler-fish, Trematodes of, [62], [72]

Anguillula aceti, [125], [154];

A. tritici, [125];

A. diplogaster, [155]

Anguillulidae, [137], [154]

Anguinella, [532]

Annadrilus, [386]

Annelida, [241]

Anocelis, [42]

Anonymidae, [19]

Anonymus, [16], [18], [19], [20];

penes, [27]

Anopla, [109]

Anoplocephala, [91];

characters, [90]:

A. mamillana, [90];

A. perfoliata, life-history, [83];

specific characters, [90]:

A. plicata, specific characters, [90]

Anoplodiscus, [73]

Anoplodium, [50];

A. parasiticum, occurrence, [45]

Antaeus, [388]

Antedon, as host, [342]

Antenna, of Rotifers, [215]

Anthobothrium, [76] n., [91]

Anthocotyle, [73]

Antinoë, [298]

Antipathes, as host, [298]

Anuraea, [225], [226]

Anuraeidae, [201], [205], [225], [226]

A'oon, an edible worm, [297]

Apel, on Priapuloidea, [433]

Aperture, of zooecium, [468], [517], [523], [524]

Aphaneura, [353], [374]

Aphanostoma, [49]

Aphanostomatidae, [49]

Aphelenchus, [131], [155], [157]

Aphrodite, [312];

shape, [258];

head, [260];

peristomium, [263];

chaetae, [268];

felting, [312];

intestine, [271];

genital cells, [273];

colour, [291]:

A. aculeata, [312];

distribution, [299];

A. echidna, [299]

Aphroditidae, [258], [309];

frontal ridge, [260];

parapodium, [264];

elytra, [266], [309];

chaetae, [266]

Apical plate, of Trochosphere, [245]

Apodina, [235]

Apodoides, [225]

Apogon, Scolex polymorphus in, [77]

Apsilidae, [201], [203], [214], [220], [221]

Apsilus, [201], [212], [213], [214], [221]

Arabellites, [302]

Arachnidium, [532]

Archiannelida, [241];

anatomy, [243] f.;

nerve cords, [255];

development, [243], [245]

Archigetes, [5], [74], [76], [91];

significance of, [77]

Area, of zooecium, [523], [524]

Arenicola, [333];

perienteric sinus, [252];

nephridium, [253], [254], [269];

prostomium, [259];

body, [259];

head, [264];

gill, [265];

chaetae, [266] f.;

genital organs, [273];

otocyst, [273];

burrows, [285];

pigment, [291];

colour, [293];

A. marina, [333];

habits, [301];

in brackish water, [284];

as bait, [297];

eggs, [314]

Arenicolidae, [258], [333]

Argilophilus, [372]

Arhynchidae, [185]

Arhynchus hemignathi, [181], [185]

Aricia, otocyst, [273];

eggs, [275]

Ariciidae, [258], [321];

gill, [265]

Aristotle, on Earthworms, [347]

Armata, [445], [446]

Arthropoda, absence of cilia in, [124]

Articulata, [517], [518]

Ascaridae, [131], [138], [163]

Ascaris, [139], [163];

A. acus, [130];

A. alata, [140];

A. depressa, [141];

A. ferox, [141];

A. incurva, [141];

A. leptoptera, [141];

A. lumbricoides, [125], [134], [135], [139], [163];

A. megalocephala, [125], [127], [128], [131], [136], [140], [163];

A. mucronata, [141];

A. mystax, [125], [130], [140];

A. nigrovenosa, [155];

A. rubicunda, [141];

A. suillae, [139];

A. sulcata, [141];

A. transfuga, [125], [126], [141]

Ascodictyon, [521] n.

Ascomorpha, [223]

Ascopodaria, [488] n.

Asellus, Rotifers attached to, [227]

Asexual reproduction, in Triclads, [40];

in Rhabdocoels, [44];

in Cestodes, [80];

in Trichoplax and Salinella, [96];

in Polychaeta, [278] f., [279], [280], [282], [340];

in Oligochaeta, [374], [375], [377];

in Polyzoa, [496], [514]

Aspidobothridae, [73]

Aspidocotyle, [73]

Aspidocotylea, [73]

Aspidogaster, [63], [73]

Aspidosiphon, [421], [423], [424], [425], [428];

commensalism of, [429]

Asplanchna, [200], [205], [210], [213], [215] n., [223], [226]

Asplanchnaceae, [203], [212], [220], [222]

Asplanchnidae, [200], [201], [203], [205], [211], [212], [216], [223], [226], [230]

Asplanchnopus, [201], [211], [222], [223], [226], [230]

Ass, parasites of, [140]

Association, of Rhabdocoels with Lamellibranchs and Sea-urchins, [45];

of Monotus fuscus with littoral animals, [46];

significance, in Turbellaria, [51]—see also Commensal and Parasitic

Asteroids, as hosts, [341]

Asterope, [315]

Astropecten, as host, [297], [309]

Atokous phase, [277] n.

Atractonema, [131], [150], [152], [153]

Atrium (genital), in Planaria, [38], [39];

in Oligochaeta, [361], [378]

Atrochus, [201], [213], [214], [221]

Auditory organs, of Turbellaria, [26];

of Hoplonemertea, [106], [110];

of Nematoda, [128];

of Polychaeta, [273]

Aulastomum, [393], [399], [403]

Auricles, of Rotifers, [205]

Autolytus, [308];

eye, [255];

denticles, [270];

brood-sac, [275], [276];

reproduction, [278], [279];

sexual dimorphism, [281];

A. ebiensis, eggs, [276]

Automolos, British species, [50]

Avenella, [533]

Avicularian zooecium, [482], [524]

Avicularium, [466], [467], [468], [482] f., [482], [516], [517], [522] f., [524];

adventitious, [482];

vicarious, [482];

vibraculoid, [484], [485];

structure, [483];

movements, [485];

function, [486]

Axine, [56], [73]

Axiothea, [332], [333]

Baely, on human parasites, [139]

Baird, on Oligochaeta, [382]

Bait, Polychaeta as, [297]

Baker, on Rotifers, [197], [207]; on Polyzoa,

496 n.

Balanoglossus, affinities of Nemertinea with, [120]

Balatro, [204], [212], [224], [227]

Balfour, on Trochosphere, [229]

Barentsia, [488] n.

Barrois, on Polyzoa, [509]

Basement-membrane, of Leptoplana, [11], [12];

of Nemertines, [102], [103], [110] f.

Bathymetrical distribution, of Polychaeta, [300]

Bdellodrilus, [376]

Bdelloida, [201], [203] f., [211], [213], [215], [216], [222], [227]

Bdellouridae, [32], [42]

Beania, [518], [525]

Beddard, on Tetrastemma aquarium dulcium, [118];

on Oligochaeta, [347] f.;

on Leeches, [392] f.

Bedwell, on Rotifers, [198]

Beneden, van, on Cestodes, [76];

on Nematodes, [162];

on Phoronis, [450]

Benham, on a fresh-water Tetrastemma, [118];

on Archiannelida, [241] f.;

on Polychaeta, [245] f.;

on Myzostomaria, [341] f.;

on Oligochaeta, [357], [373], [382];

on Phoronis, [452] f.

Benhamia, [383] f.

Bicellaria, [481], [518], [526], [527]

Bilfinger, on Rotifers, [212]

Bilharzia, [4], [73];

B. crassa, [70];

B. haematobia, [63], [68] f., [69]

Bimastos, [389]

Bipaliidae, [35], [42]

Bipalium, [33], [34], [42], [408]

Birds, Trematodes of, [62], [63], [64], [72];

Cestodes of, [77] f., [84], [85];

Nematodes of, [144], [149], [163];

Gordius of, [173];

Acanthocephala of, [184], [185]

Bisexual, Turbellaria, [44];

Trematodes, [70] f.

Bladder, of Rotifers, [214]

Bladder-worms, [5], [79] f., [89]

Blanchard, on Cestoda, [91];

on Hirudinea, [392] f., [405], [408]

Blastomeres, of egg of Distomum, [65]

Blood, of Nemertinea, [108];

of Polygordius, [244];

of Chaetopoda, [252];

of Chlorhaemidae, [252], [334];

of Magelona, [252], [325];

of Sabelliformia, [252], [337]

Blood-corpuscles, in Chaetopoda, [252]

Body-cavity (including Coelom), of Nematoda, [130];

of Gordius, [166];

of Acanthocephala, [175], [178];

of Chaetognatha, [187];

of Archiannelids, [243], [244];

of Polychaeta, [249];

of Myzostoma, [343];

of Oligochaeta, [355];

of Leeches, [397];

of Gephyrea, [416];

of Phoronis, [454], [462];

of Polyzoa, [468], [488], [495]

Body-wall, of Nemertinea, [102], [103];

of Nematodes, [125];

of Gordiidae, [165];

of Acanthocephala, [175];

of Chaetognatha, [187];

of Rotifers, [205];

of Nereis, [249];

of Oligochaeta, [349];

of Gephyrea, [414], [436];

of Phoronis, [454];

of Polyzoa, [470], [495], [500]

Bohadsch, on Gephyrea, [411]

Bohemilla, [377];

chaeta, [350]

Bonellein, [435], [292]

Bonellia, [411], [434], [442];

anatomy, [434] f., [435];

male, [438];

development, [439];

habits of, [442];

as host, [297]

Bonnet, on Oligochaeta, [348], [379]

Boring Worms, [286], [287]

Borlase, on Lineus marinus, [99]

Borlasia elizabethae, [111], [114]

Bothriocephalidae, [91]

Bothriocephalinae, [91]

Bothriocephalus, [91];

B. cordatus, [81], [91];

B. cristatus, [81], [91];

B. latus, in man, [81], [91];

life-history, [84];

reproductive organs, [87] f.;

larva, [87];

B. mansoni (= B. liguloides), [81], [91]

Bothriocerca, [226]

Bothrioneuron, [379]

Bothrioplana, [46], [50]

Bothrioplanidae, [42], [46], [50]

Bothromesostoma personatum, [49]

Bourne, on Oligochaeta, [352], [373], [377] n., [380];

on Leeches, [400]

Bouvier, on commensal Gephyrea, [429]

Bowerbankia, [470], [480], [481], [492], [500], [518], [532], [533];

larva, [511], [513];

budding, [514]

Brachionidae, [225]

Brachionus, [200], [201], [204], [218], [225], [226], [227]

Brachydrilus, [357]

Brackish water, Rotifers, [226];

Polychaeta, [284];

Polyzoa, [492]

Bradynema, [150], [151], [160]

Braem, on statoblasts, [503] f.

Brain—see Nervous System

Branchellion, [393], [395], [397], [401], [406]

Branchial crown, [336];

regeneration of, [283]

Branchiobdella, [376]

Branchiomma, [337];

gills, [261];

eyes, [272];

B. vigilans on Aphrodite, [299]

Branchiura, [352], [361], [367], [378] f.;

transverse section, [353]

Braun, on Platyhelminthes, etc., [6] n., [55] n., [62], [94]

Brettia, [525], [527]

Bristles = Chaetae, q.v.

Bristle-worms, [241]

British, Polycladida, [19];

Tricladida, [42];

Rhabdocoelida, [49];

Nemertinea, [100], [110] f.;

Polychaeta, [306] f.;

Earthworms, [390];

Leeches, [393];

Gephyrea, [449];

Polyzoa, [488] n., [505], [523] f.

Brood-pouch, of Spirorbis, [261], [276], [341];

of Salmacina, [276];

of Entoprocta, [487], [507]

Brood-sac, of Autolytus, [275];

of Myrianida, [280]

Brown body, in Polyzoa, [468], [471] f., [472], [489], [496], [510], [514]

Brown tubes (nephridia), of Sipunculoidea, [415], [417], [423], [425];

of Echiuroidea, [435], [437], [439], [441];

of Epithetosomatoidea, [445];

used as generative ducts, [418], [438];

absent in Priapuloidea, [430]

Bryozoa, [475]

Buccal region, in Polychaeta, [249], [250], [269];

of Nereis diversicolor, [248];

of N. cultrifera, [316]

Buchanan, on marine muds, [423]

Buchholzia, [359]

Budding, in Syllidae, [279], [283] (see also Gemmation);

in Polyzoa, [467], [514] (see also Polypide-bud)

Bugula, [467], [468], [477], [481], [515], [517], [518], [519], [526];

avicularia, [483], [485];

larva, [511]

Bunge, on respiration in Nematoda, [130]

Bürger, on Nemertinea, [109], [112];

on Nectonema, [168];

on Hirudinea, [397], [403]

Burrows, of Polychaeta, [285], [304];

of Cirratulus, [286];

of Nereis, [286], [316], [317];

of Arenicola, [333];

fossil, [302];

of Earthworms, [368];

of Sipunculus, [426]

Bursa seminalis, in Rhabdocoels, [48]

Busk, on Polyzoa, [465] n., [475], [487], [519]

Buskia, [533]

Bütschli, on Nematoda, [137]

Byrsophlebs, occurrence, [44];

British species, [49]

Caberea, [487], [518], [526];

vibracula, [486], [517]

Caecum, in Polyzoa, [499]

Calathus, host of Gordius, [172]

Calceostominae, [73]

Calceostomum, [73]

Caldwell, on Phoronis, [454], [456], [461]

Calicotyle, [73]

Callidina, [201], [202], [204], [218], [219], [222], [225], [227], [230]

Calliobothrium, [76] n., [91];

larva, [77]

Calotte, of Dicyemids, [93]

Calyx, [488]

Camerano, on development of Gordius, [170]

Capitella, [331];

peristomium, [263];

special chaetae, [267], [268];

habitat, [286];

colour, [291];

O. capitata, distribution, [299]

Capitellidae, [258], [331], [373]

Capitelliformia, [258], [305];

guanin in, [253];

body, [259];

buccal region, [269];

siphon, [272];

ciliated organs, [272], [273];

genital organs, [273]

Carabus, host of Gordius, [172]

Carinella, [112];

British species, [112]

Carinellidae, side organs of, [107]

Caruncle, of Amphinomidae, [260], [273] n., [318]

Caryophyllaeus, [91];

C. mutabilis, [77]

Castalia, [308];

distribution of, [300]

Castings, of Polychaeta, [285];

fossil, [302];

of Arenicola, [333]

Castrada, [44], [49]

Cat, parasites of, [80], [125], [130], [140], [143], [144], [145]

Catenicella, [518], [519]

Catenula, [49]

Cathypna, [225]

Cathypnidae, [225]

Cellaria, [479], [515], [518], [519], [526];

zooecia and avicularium, [482]

Cellepora, [518], [527], [528], [529];

avicularia, [483], [517]

Celleporella, [529]

Cellularia, [518], [527]

Cellularina, [518]

Cement-glands, of Rotifers, [205]

Cephalic slits, of Nemertinea, [101], [104], [107], [111], [112]

Cephalisation, in Polychaeta, [263];

in Oligochaeta, [377]

Cephalodiscus, [461] f.

Cephalopods, parasites of, [78], [92];

list of, containing Dicyemids, [94]

Cephalosiphon, [205], [221]

Cephalothrix, [112]

Cercaria, [13], [65], [67], [71] f.;

C. macrocerca, [72];

C. cystophora, [72]

Cercyra, [42]

Cerebral organ, of Nemertinea, [107];

of Gephyrea, [417]

Cerebratulus, [101], [111], [114];

British species, [111]

Cerfontaine, on Earthworms, [349], [350]

Cestoda, characters of the group, [5], [74];

nature of, [76] f.;

occurrence, [77]-82;

life-histories, [83];

structure and development, [84]-89;

synoptic table of, [89] f.;

classification, [91]

Cestodariidae (= Monozoa), [91]

Cestoplana, [17], [18], [19]

Cestoplanidae, [19]

Chaetae, [241];

of Polychaeta, [266], [267];

provisional, [274];

of Nereis, [246], [247];

of Heteronereid, [276], [277];

jointed, [246];

natatory, in sexual Syllid, [278], [307];

iridescent, [268], [291], [312];

palmate, of Coabangia, [339] n.;

colour, [291];

genital, of Capitella, [331];

of Sternaspis, [336];

special, of Polydora, [261], [267];

of Chaetopterus, [267], [324];

of Myzostoma, [342];

of Oligochaeta, [347], [350], [351], [352];

penial, [362];

of Microdrili, [375] f.;

of Megadrili, [381] f.;

of Lumbricidae, [389], [390];

of Leeches, [395], [396];

(= hooks), of Echiuroid Gephyrea, [434], [435], [438], [440] f., [446]

Chaetifera, [445], [446]

Chaetobranchus, [352]

Chaetogaster, [356], [377], [401]

Chaetognatha, [186] f., [534];

anatomy, [186];

development, [189];

habits, [189];

classification, [191];

key to, [193];

American species, [534]

Chaetonotus, [232], [235]

Chaetopoda, [241] f.;

as food for Nemertinea, [115]

Chaetopteridae, [258], [323]

Chaetopterus, [304] n., [323];

anatomy, [323] f.;

special chaetae, [267];

larva, [274], [325];

pigment, [292];

phosphorescence, [295], [296];

commensals of, [298], [478], [533];

Ch. variopedatus, [324]

Chaetosoma, [158]

Chaetosomatidae, [158]

Chaetosyllis, form of head, [278]

Chaetozone, [326];

uncini, [268]

Chaetura, [235]

Chalk, Serpulids of, [301]

Charles, on male guinea-worm, [148]

Cheilostomata, [477], [506], [518], [519], [525], [526] f.;

occurrence, [478];

external characters (see also Avicularium and Vibraculum), [481];

ovicells, [507];

reproduction, [507] f.;

larva, [511];

fossil, [521]

Chiaje, Delle, on Gephyrea, [411]

Chickoff, on Triclads, [41]

Chironomus, host of Gordius, [172]

Chitin, [249], [267];

in coelomic corpuscles, [252]

Chloeia, colour, [291]

Chlorhaemidae, [258], [305], [334], [336];

chlorocruorin in, [252];

head, [260], [262], [264];

palps, [260];

tentacles, [262]

Chlorocruorin, [252], [334];

colour due to, [291]

Chone, [338]

Chorizopora, [530]

Cilia, [3];

of Leptoplana, [10], [11], [12], [15];

of Polyclads, [23], [25], [26];

of Müller's larva, [29];

of Land Planarians, [33];

of Planaria lactea, [35];

of Temnocephala, [53];

of Trematode-larvae, [3], [59], [60], [65];

of Cestode-larvae, [87];

absent in certain groups, [124], [396];

of Rotifers, [202] f.;

of Archiannelida, [243], [244];

of Echiuroidea, [434];

of Phoronis, [453];

of Polyzoa, [467], [470]

Ciliated, lappets, of Pterosyllis, [273] n.;

pits, of Polygordius, [244];

pits (= nuchal organs), of Polychaeta, [272] f.;

organs, of Capitelliformia, [305]

Cingulum, in Rotifers, [202]

Cirratulidae, [258], [325];

gill, [265];

tentacular filaments, [304] n.

Cirratulus, [326];

burrows, [286];

pigment, [292];

colour, [293];

viviparous, [276];

C. tentaculatus, [326]

Cirri, of Nereis, [246];

of Polychaeta, [265];

of Myzostoma, [342];

anal, [259];

nuchal, of Eunicidae, [318];

peristomial, of Nereis, [248];

nerves to, [254];

of Polychaeta, [263]

Cladocora, with Myxicola, [294]

Claparède, on Heteronereis, [276], [277];

on Earthworms, [347], [355], [356]

Claus, on Nematoda, [138];

on Seisonaceae, [225] n.

Clepsine—see Glossiphonia

Clitellio, [366], [378]

Cloeosiphon, [424], [425], [429]

Clover sickness, [155]

Clymene, [333];

C. ebiensis, tube of, [287]

Clymenidae—see Maldanidae

Coabangia, [284], [339] n.

Cobb, on Nematoda, [131] n., [138]

Cobbold, on Nematoda, [140]

Cobitis, host of Gordius, [173]

Cochleare, [225]

Cocoons, of Triclads, [40];

of Oligochaeta, [364], [365];

of Leeches, [404]

Coelom—see Body-cavity

Coelomic fluid, of Polychaeta, [252];

as cause of colour, [291]

Coelopus, [225]

Cohn, on Rotifers, [198]

Collar, peristomial, of Sabellidae, [336];

of Gephyrea, [421];

of Ctenostomata, [470], [477], [480], [481]

Colonial nervous system, [471]

Colony, of Myrianida, [281];

of Syllis ramosa, [282];

of Polyzoa, [466]

Colour of Polyclads, [20];

of Land Planarians, [33];

of Nemertinea, [102];

of Polychaeta, [291], [314], [340]

Coluridae, [207], [225]

Colurus, [225], [226]

Comatula, as host, [342]

Commensal, Polychaeta, [297] f., [323], [325];

Gephyrea, [428], [429];

Polyzoa, [489]

Conn, on development of Gephyrea, [419] n., [441], [444], [447]

Conoceros, [19]

Conochilus, [202], [203], [205], [215], [221], [226]

Conocyema, hosts of, [94]

Convoluta, [45];

British species, [43], [49];

C. henseni, pelagic habit, [43];

C. roscoffensis, assimilating tissue, [43]

Copepoda, on Polychaeta, [299]

Copeus, [215], [224]

Coral reefs, Polychaeta in, [293]

Corallina (= Coralline Alga), [14], [488], [516]

Coralline, [465]

Coralline Crag, [465], [521]

Corallobothrium, [91]

Corethra, host of Gordius, [172]

Cori, on Phoronis, [451] f.

Cornulites, [302]

Cotylea, [16] f., [17], [18]

Cotylogaster, [73]

Cotyloplana, [35]

Crateromorpha, as host, [282]

Crayfish, Temnocephala associated with, [53]

Creeper, [317]

Crepina, [450]

Cretaceous, Polyzoa, [520], [521]

Cribrilina, [518], [524], [528]

Crinoids, as hosts, [341]

Criodrilus, [358], [366], [386]

Crisia, [471], [478], [479], [480], [507], [518], [531]

Crisiidae, [517]

Crisp, on Parasites, [164]

Cristatella, [494] f., [495], [499], [501], [503]-505, [512], [518];

attacked by Planarians, [486];

movements, [494], [496], [498];

fission, [496], [506];

statoblast, [502], [503];

larva, [512]

Crossopodia, [302]

Crotchets, [266], [267], [305], [322]

Crustacea, parasites of, [174], [179], [182]

Cryptocelis, [19], [24]

Cryptocephala, [258], [303], [305];

vascular system, [252];

prostomium, [259];

tentacles, [263];

eyes, [272];

food, [296]

Cryptodrilidae, [357], [362], [373], [382]

Cryptodrilus, [372], [382] f.

Ctenodrilus, [373]

Ctenophores, as hosts, [298]

Ctenostomata, [470], [477], [479], [480], [518], [532];

occurrence, [478];

in fresh water, [492];

external characters, [480];

reproduction, [507];

larva, [511];

relation to Phylactolaemata, [493], [502] f.;

fossil, [521] n.

Cucullanus, [136], [142], [163];

C. elegans, [143], [161]

Cucumaria, as host, [298]

Cuénot, on Gephyrea, [416] n.

Cuticle, of Nemathelminthes, [125], [165], [175];

of Rotifera, etc., [205], [233], [236];

of Polyzoa, [470]—see also Epidermis

Cuvier, on Oligochaeta, [352];

on Gephyrea, [411]

Cyclatella, [489]

Cyclicobdella, [392]

Cycloporus, [19], [22], [24]

Cyclops, parasites of, [143], [148], [161]

Cyclorhagae, [238]

Cyclostomata, [477], [479], [506], [517], [518], [525], [531];

occurrence, [478];

external characters, [480];

ovicells, [507];

reproduction, [507], [511];

larva, [511]; fossil, [520], [521]

Cydippe, as host, [298]

Cylindroecium, [533]

Cylindrostoma, [46];

British species, [50]

Cyphonautes, [509], [510], [512], [520]

Cyprina, Malacobdella found on, [119]

Cyrtonia, [224]

Cyst, of Land-Planarians, [33];

of Myzostoma, [342], [343], [344];

(capsules), of Aeolosoma, [370], [375]

Cystibranchus, [395], [406]

Cysticercoid-larva, [83], [85], [88]

Cysticercus-larva, [79], [80];

list of, [83];

C. cellulosae, [79], [80];

C. pisiformis, development, [81], [85], [89]

Cysticolous, Myzostomaria, [344]

Cystoidotaeninae, [91]

Cystotaeninae, [91]

Dactylogyrus, [73]

Dalyell, on habits of Turbellaria, [6], [10], [20];

on regeneration in Polychaeta, [283];

on tubes of Polychaeta, [287];

on Hirudinea, [405] n.;

on larvae of Flustra, [466];

on Cristatella, [496]

Danielssen and Koren, on Gephyrea, [442], [444]

Daphnia, Rotifers attached to, [227]

Dapidia, [225]

Darwin, on Earthworms, [354], [359], [368]

Dasybranchus, [331];

gill, [268]

Dasychone, [338];

gills, [261];

eyes, [272];

regeneration, [283]

Dasydetes, [232], [235]

Davaine, on Nematoda, [140], [145]

Davainea, [91];

D. friedbergeri, [84];

D. madagascariensis, [80], [84];

D. proglottina, life-history, [84]

Davenport, on Urnatella, [491]

Davis, on Rotifers, [227]

Deep-sea, Polychaeta, [300];

Polyzoa, [478]

Deinodrilus, [351], [384]

Delagia, [478] n.

Dendrobaena, [382]

Dendrocoelum, [30], [35], [39]

Dendrostoma, [422], [425], [428]

Dendy, on Land Planarians, [33], [34], [38]

Denticles, [248], [250], [316], [522]

Dero, [352], [377]

Derostoma, [44], [50]

Desmogaster, [380]

Desmoscolecidae, [159]

Desmoscolex, [159], [258]

Desor, on Nemertine development, [99];

Type of, larva, [113]

Development, of Polyclads, [28];

of Nemertinea, [99], [113];

of Nematoda, [135];

of Gordius, [171];

of Acanthocephala, [179];

of Chaetognatha, [189];

of Rotifers, [218];

of Archiannelida, [243], [245];

of Polychaeta, [274] f.;

of Oligochaeta, [365];

of Leeches, [399];

of Gephyrea, [419], [432], [439], [447];

of Phoronis, [458];

of Polyzoa, [506], [509]—see also Life-history and Larva

Diachaeta, [366]

Diaphragm, of Nereis introvert, [250], [251];

of Terebellidae, [304], [327];

of Polyzoa, [469], [470], [500], [508]

Diaschiza, [225], [226]

Diastopora, [518], [531]

Dichogaster, [362], [383]

Diclidophora, [73]

Dicotylus, [32], [35], [36], [42]

Dicranotaenia, [91];

D. coronula, life-history, [84]

Dicyema, [93];

vermiform larva of, [92];

hosts of, [94]

Dicyemennea, [93], [93];

hosts of, [94]

Dicyemidae, [92] f.

Didymogaster, [383]

Didymozoon, [73];

D. thynni (= Monostomum bipartitum), [71]

Didymozoontidae, [73]

Digaster, [358], [359], [382] f.

Digenea (Digenetic Trematodes), [5], [52], [62], [73];

occurrence and habits, [62];

life-histories, [63] f., [71] f.

Digestive system, of Leptoplana, [11], [12];

of Polyclads, [24];

of Triclads, [37], [39];

of Rhabdocoelida, [42] f.;

of Temnocephala, [53], [54];

of Polystomum, [57];

of Distomum, [62];

absence of, in Cestodes, [74];

of Nemertinea, [103], [103], [104];

of Nematoda, [130];

of Gordiidae, [166], [169];

of Chaetognatha, [187];

of Rotifers, etc., [209], [233], [237];

of Archiannelida, [243];

of Polychaeta, [249], [269];

of Oligochaeta, [358];

of Hirudinea, [396];

of Gephyrea, [414];

of Phoronis, [454];

of Polyzoa, [468], [469], [487]

Digitibranchus, [353]

Diglena, [212], [217], [224], [226]

Digonopora, [16]

Dimorphism, in Polystomum, [59];

sexual, of Trematodes, [70];

of Orthonectida, [95];

of Dinophilus, [243];

of Polychaeta, [276], [279] f.;

of Gephyrea, [438]

Dinocharididae, [225]

Dinocharis, [225]

Dinophilus, [242];

D. taeniatus, [242];

D. gyrociliatus, sexual dimorphism, [243]

Dinops, [223]

Diopatra, gill, [318]

Diphyllinae, [91]

Diplax, [225]

Diplectanum, [73]

Diplobothrium, [73]

Diplocardia, [385]

Diplodiscus, [73];

D. (Amphistomum) subclavatum, life-history, [71]

Diplogaster, [154]

Diplois, [225]

Diplostomum, [73]

Diplozoon, [55], [60], [73];

life-history, [60], [61];

reproductive organs, [60]

Diporochaeta, [381]

Diporpa, [60], [61]

Diporula, [528]

Dipylidium, [81], [91];

life-history, [83], [88], [89];

specific characters, [90]

Disc, in Rotifers, [200], [202] f., [202]

Discharge, of genital cells;

Nemertinea, [116];

Archiannelida, [244];

Polychaeta, [256], [274], [275]

Discobdella, [226]

Discocelis, [19], [23]

Discodrilidae, [350], [376], [392], [395]

Discopus, [201], [222], [226], [227]

Dispharagus, [147], [149], [163]

Dispinthera, [225]

Distemma, [212], [224], [226]

Distomatidae, [73]

Distomum advena (= D. migrans), life-history, [71];

D. appendiculatum, life-history, [71];

D. ascidia, life-history, [71];

D. atriventre, life-history, [71];

D. brachysomum, life-history, [71];

D. buskii, [63];

D. caudatum, life-history, [71];

D. clavigerum, life-history, [72];

D. conjunctum, [63];

D. crassum, [63];

D. cygnoides, life-history, [72];

D. cylindraceum, [72];

D. dimorphum, [72];

D. echinatum, [63];

life-history, [72];

D. echiuri, [444];

D. endolobum, life-history, [72];

D. excavatum, [63];

D. ferox, [63];

D. globiporum, life-history, [72];

D. hians, [63];

D. hepaticum (liver-fluke), [3], [63], [67] f.,72;

D. heterophyes, [63];

D. hystrix, life-history, [72];

D. japonicum (= D. spathulatum), [63];

D. lanceolatum, [63];

D. luteum, excretory system of, [62];

D. macrostomum, life-history, [64], [65], [72];

D. magnum, [68];

D. militare, life-history, [72];

D. nodulosum, life-history, [72];

D. oculi-humani (= D. ophthalmobium), [63];

D. ovocaudatum, life-history, [72];

D. pulmonale, [63], [70];

D. rathouisi, [63], [70];

D. retusum, life-history, [72];

D. ringeri (= D. pulmonale), [63];

D. signatum, life-history, [72];

D. sinense, [70]; D. spathulatum, [63];

D. squamula, life-history, [72];

D. trigonocephalum, life-history, [72];

D. westermanni (= D. pulmonale), [63]

Distyla, [225]

Dithyridium, [91]

Ditrupa, [301]

Diurella, [225], [226]

Dochmius, [133], [135], [142], [160], [163];

D. cernua, [143];

D. duodenalis, [143], [163];

D. stenocephala, [143];

D. trigonocephala, [143]

Dodecaceria, [287], [326], [327]

Dog, parasites of, [80] f., [90], [125], [140], [142], [143], [145]

Dolichoplana, [37], [42]

Domestic animals, Trematodes of, [67], [68], [70], [72];

Cestodes of, [81], [89];

Nematodes of, [139] f., [163];

Acanthocephala of, [184]

Domopora, [531], [532]

Dorsal ciliated organ, [247], [254], [256]

Dorsal pores, [348]

Dorylaimus, [131], [157], [160]

Dracunculus, [131], [135], [147]

Drepanidotaenia, [91];

D. anatina, life-history, [84], [85];

D. gracilis, D. infundibuliformis, D. setigera, life-history, [84]

Drepanophorus, excretory system, [108];

British species, [110]

Drilophagidae, [224]

Drilophagus, [204], [210], [212], [224], [227]

Dugès, on Planarians, [6], [10];

on Oligochaeta, [368]

Dujardin, on Rotifers, [198];

on Gastrotricha, [231];

on Kinorhyncha, [236]

Duplicature, [499], [500]

Duthiersia, [91]

Dwarf males, of Myzostoma, [344];

of Gephyrea, [438]

Ear-cockle, [155]

Earthworms, [347], [365];

senses, [354];

food, [359];

effect on the soil, [368];

distribution, [369] f.;

classification, [380] f.;

British, [390]—see also Oligochaeta

Ebrard, on Hirudinea, [393]

Echeneibothrium, [91]

Echinella, [73]

Echinobothrium, [74], [75], [85], [91]

Echinococcus, [80], [83]

Echinocotyle, [91]

Echinoderes, [236] f., [236]

Echinorhynchidae, [182]

Echinorhynchus acus, [175], [179];

E. angustatus, [174], [183];

E. clavula, [183];

E. haeruca, [176];

E. linstowi, [183];

E. lutzii, [183];

E. moniliformis, [183];

E. proteus, [174], [180], [181], [182], [182]

Echinosiphon, [424], [429]

Echiuroidea, [241] n., [412], [434], [446];

anatomy, [434] f.;

classification, [440];

development, [439];

parasites, [444];

habits, [442]

Echiurus, [336], [411], [435], [440], [441];

development, [439]

Eckstein, on Rotifers, [198]

Eclipidrilus, [380]

Economic uses, of Polychaeta, [296], [297]

Ectocyst, [469], [470], [523];

of Phylactolaemata, [496] f., [503]

Ectoderm, of Mesozoa, [93], [95]

Ectoparasitic Trematodes, [4], [52], [53]

Ectoprocta, [475], [518];

structure, [469];

lophophore, [476];

reproduction, [506] f.;

larva, [509], [510], [511];

compared with Entoprocta, [488]

Effects, of parasites on their hosts, [56], [68], [69], [80], [94], [162]

Eggs, of Leptoplana, [10], [16];

of Polyclads, [28];

of Triclads, [33], [40];

of Rhabdocoels, [47], [48];

of Termatodes, [52];

of ectoparasitic Trematodes, [54], [58], [60], [61];

of endoparasitic Trematodes, [63], [69];

of Cestodes, [87];

of Orthonectidae, [95];

of Nemertinea, [116];

of Nematoda, [135], [162];

of Gordius, [171];

of Acanthocephala, [179];

of Chaetognatha, [189];

of Rotifera, [200], [216] f.;

of Gastrotricha, [234];

of Nereis, [256];

of Polychaeta, [274], [275];

of Phyllodocids, [314];

of Scoloplos, [321];

of Myzostoma, [343];

of Polyzoa, [506], [507]

Ehrenberg, on Turbellaria, [3], [6];

on Rotifers, [198], [220] n., [228];

on Gastrotricha, [231];

on Polyzoa (Bryozoa), [475]

Eichhorn, on Rotifers, [197]

Eisen, on Oligochaeta, [380], [390]

Eisig, on Capitellidae, [373];

on Bonellia, [443]

Electra, [481], [518], [523], [530];

larva, [509], [510];

variation, [516]

Elytra, of Polynoids, [265], [292], [294], [298], [299], [309], [310], [311];

phosphorescent, [295], [296];

as brood-pouch, [275];

of Aphroditidae, [266];

arrangement of, [309];

of Sigalionina, [313]

Enantia, [16] n., [19]

Enantiidae, [19]

Enchelidium, [157]

Enchytraeidae, [359], [360], [361], [366], [367], [370], [375]

Enchytraeus, host of Gordius, [173]

Encotylabe, [73];

eggs of E. pagelli, [58]

Endocyst, [471]

Endoderm, of Mesozoa, [93], [95]

Endoparasitic Trematodes, [4], [52], [62]

Enopla, [109]

Enoplidae, [157]

Enoplus, [157], [160]

Entalophora, [518], [532]

Enteroploea, [224]

Enterostoma, [46];

British species, [50]

Entoprocta, [475], [479], [487] f., [518];

lophophore, [476];

reproduction, [506];

larva, [509], [510]

Eosphora, [216], [218], [224]

Ephemera, host of Gordius, [172], [173]

Ephesia, [321]

Epibdella, [55], [73]

Epidermis, of Leptoplana, [11], [12];

of Polyclads, [20], [25], [29];

of Trematodes, [56];

of Cestodes, [85];

of Nemertinea, [102];

of Nematoda, [125];

of Acanthocephala, [175];

of Nereis, [249];

of Oligochaeta, [349];

of Leeches, [396];

of Gephyrea, [414];

of Phoronis, [454]—see also Hypodermis

Epigamous, phase, of Nereis, [277] n.;

worms, [281]

Epistome, in Phoronis, [453], [455];

in Phylactolaemata, [476], [476], [499];

in larva of Loxosoma, [509]

Epistomia, [518], [526]

Epithetosoma, [444], [445], [449]

Epithetosomatoidea, [412], [444]

Epitokous, phase, of Nereis, [277] n.

Eretmia, [225], [226]

Eriographidae, [258], [338]

Erpocotyle, [73]

Errantia, [258], [285]

Eschara, [516]

Escharina, [518]

Escharoides, [527]

Euchlanididae, [225]

Euchlanis, [225], [226]

Eucratea, [518], [525], [527], [528]

Eudrilidae, [359], [360], [380], [385], [403] f.

Eudrilus, [354], [385], [403] f.

Euichthydina, [235]

Eulalia viridis, [314];

pigment, [292];

colour, [293];

eggs, [314] n.

Eumenia, [334]

Eunice, [318], [319];

nephridium, [254];

eye, [255];

head, [262];

parapodium, [264];

gill, [265];

chaetae, [266], [267];

jaws, [270];

substance of tube, [290];

commensal, [298];

E. tibiana, [290]

Eunicidae, [258], [318];

palps, [260];

tentacles, [262];

jaws, [270];

tube, [285], [290];

colour, [291], [292];

parasitic, [297];

tubes containing Polynoids, [298];

Palaeozoic, [302]

Eunicites, [301], [302]

Euphrosyne, [318];

parapodium, [265];

chaetae, [267]

Eupolia, [113]

Eupolyzoa, [461]

Eurycercus, shell of, inhabited by Rotifers, [227] n.

Eurylepta, [19]

Euryleptidae, [19]

Eurythoe, [318]

Eustrongylus gigas, [142];

E. tubifex, [142]

Eusyllis, reproduction of, [278]

Excretion, as cause of colour, [291]

Excretory system, of Leptoplana, [13];

of Polyclads, [25];

of Triclads, [41];

absent in Acoela, [42];

of Temnocephala, [54];

of Digenea, [62];

of Cestodes, [86];

of Nemertinea, [108], [108], [120];

of Nematodes, [133];

of Acanthocephala, [177];

of Rotifers, [199], [213];

of Gastrotricha, [234];

of Kinorhyncha, [237];

of Polychaeta, [253];

of Polyzoa, [472] f.—see also Nephridium

Exogone, [308];

attachment of eggs, [275];

reproduction, [278]

Eyes, of Leptoplana, [8], [15];

of Polyclads, [26], [27];

development of, [30];

of larval Polystomatidae, [59], [60];

of Nemertinea, [102], [106];

of Nematodes, [128];

of Gordius, [166];

of Chaetognatha, [188];

of Rotifera, [215];

of Gastrotricha, [234];

of Kinorhyncha, [238];

of Polychaeta, [255], [272], [314], [337], [339];

of Oligochaeta, [354];

of Leeches, [393], [394], [395];

of Gephyrea, [417];

of Polyzoon larva, [509]

Fabricia, [339];

eyes, [272];

otocyst, [273]

Faecal groove, of Sabellids, [337]

Fans, of Chaetopterus, [295], [324]

Faraday, on asexual reproduction of Planariae, [6], [40] n.

Farre, on Polyzoa, [500], [508]

Farrella, [500], [518], [533]

Fasciola, [67]

Fecampia, life-history, [45]

Felt, of Aphrodite, [268], [312]

Fertilisation, of Nemertinea, [117];

of Nematodes, [135];

of Gordiidae, [171];

of Acanthocephala, [179];

of Chaetognatha, [188];

of Rotifers, [217]

Filaria, [147], [163];

F. attenuata, [134];

F. cystica, [142];

F. denticulata, [125];

F. immitis, [148];

F. labiata, [163];

F. laticaudata, [125];

F. loa, [149];

F. medinensis, [147], [157], [163];

F. sanguinis hominis, [149], [163];

F. papillosa, [163]

Filariidae, [147]

Filigrana, [340];

fission in, [281];

tubes, [290]

Fimbria tenuis, [157]

Fischer, on branchiae in Gephyrea, [416] n.

Fishes, Trematodes of, [4], [53], [55], [62], [64], [71], [72];

Cestodes of, [77], [84], [85];

Nemathelminthes of, [142], [143], [149], [163], [173], [182]

Fission, in Bipalium, [34];

in Planariae, [40];

in Trichoplax, [96];

in Salinella, [96];

in Polychaeta, [278] f., [279], [280], [282], [340];

in Oligochaeta, [374], [375], [377];

in Phylactolaemata, [496];

in embryos, [365], [511]

Fissurella, as host, [298]

Flabelligera, [334]

Flame-cells, in Leptoplana, [13];

in Thysanozoon, [25];

in Triclads, [41];

in Temnocephala, [54];

in Polystomatidae and Tristomatidae, [56];

in Distomum luteum, [62];

in Cestodes, [86];

in Nemertinea, [108], [109];

in Rotifers, [213];

in Urnatella, [491]

Fletcherodrilus, [382]

Floscularia, [200], [203], [205], [220], [221], [226]

Flosculariaceae, [202], [211], [213], [220]

Flosculariidae, [201], [203], [205], [220] n., [221], [230]

Flukes, [51]

Flustra, [465], [466], [467], [472], [473], [477], [515], [518], [526];

avicularia, [482]

Flustrella, [467], [477], [518], [532];

larva, [513]

Flustrina, [518]

Food, of Turbellaria, [4];

of Leptoplana, [10];

of Polyclads, [24];

of Triclads, [37];

of Acoela, [43] f.;

of Rhabdocoela, [45];

of Trematodes, [4], [52], [62];

of Temnocephala, [53];

of Cestoda, [5];

of Nemertinea, [115];

of Nematodes, [131];

of Acanthocephala, [177];

of Chaetognatha, [190];

of Rotifera, [207], [212];

of Gastrotricha, [234];

of Polychaeta, [296];

of Earthworms, [359];

of Leeches, [393], [406] f.;

of Gephyrea, [422], [443];

of Polyzoa, [467]

Foot, in Rotifers, [200], [201]

Foraminifera, as food of Polychaeta, [296]

Forceps, of Eunice, [270]

Forcipate, [210], [211]

Formula, for Nematoda, [138]

Fornix, [481], [517], [525]

Fossil, Polychaeta, [301];

Polyzoa, [520];

Nemertinea, absence of, [119]

Fredericella, [476], [494], [502]-505, [518], [519];

lophophore, [495];

statoblast, [502], [503]

Frenzel, on Trematoda, [62];

on Salinella, [96]

Fresh-water, Turbellaria, compared with marine, [46];

Nemertinea, [101], [118];

Polychaeta, [284];

Polyzoa, [492]

Friend, on Oligochaeta, [388] n.

Frogs, Trematodes of, [55], [58], [62], [71] f.;

Nematodes of, [140], [142], [160], [173]

Frontal organ, of Nemertinea, [107]

Frontal palps, of Eunicidae, [318] f.

Frontal ridge, [260]

Frullania, inhabited by Rotifers, [227]

Fulcrum, in Rotifers, [210]

Funicular tissue, [471]

Funiculus, [469], [471], [472], [499], [501]

Furcularia, [216], [224], [226]

Gamble, on Platyhelminthes, [3] f.;

on Mesozoa, [92] f.

Gammarus, Rotifers attached to, [227]

Gapes, cause of, [144]

Gardiner, on development of Acoela, [44] n.

Gasterostomatidae, [73]

Gasterostomum, [73];

G. fimbriatum, life-history, [72];

G. gracilescens, [72]

Gastrocotyle, [73]

Gastrodiscus, [73]

Gastrothylax, [73]

Gastrotricha, [231] f.

Gegenbaur, on Nemertine development, [99]

Gemellaria, [518], [526]

Gemmation, [281];

in Syllidae, [278] f., [279], [280]

Geobia, [37]

Geodesmus, [34], [42]

Geographical distribution, of Turbellaria, [32] f.;

of Nemertinea, [117];

of Chaetognatha, [191], [534];

of Gastrotricha, [235];

of Polychaeta, [299] f.;

of Oligochaeta, [369] f.;

of Leeches, [405];

of Gephyrea, [426] f., [432], [441] f.;

of Phoronis, [460];

of Polyzoa, [492] f., [504], [519]

Geonemertes, [101];

description of G. chalicophora, [117]

Geoplana, [33], [38], [42]

Geoplanidae, [35], [42]

Geoscolicidae, [351], [362], [386]

Gephyrea, [411] f.;

history, [411];

external characters, [412], [420] f., [430] f., [434] f., [444];

body-wall, [414], [436];

digestive system, [414], [422], [430], [436], [445];

vascular system, [415], [421], [436];

respiratory system, [416];

body-cavity, [416], [437], [445];

nervous system, [416], [431], [437], [445];

excretory system, [417], [423], [431], [437], [445];

reproductive system, [418], [431], [437], [445];

development, [419], [439];

food, [422], [443];

commensalism, [429];

affinities, [241] n., [336], [445] f., [512];

British, [449]

Germarium, of Rotifers, [216]

Germ-yolk-gland, [47]

Giard, on Oligochaeta, [368]

Gid, induced by Coenurus, [82]

Gigantorhynchidae, [183]

Gigantorhynchus gigas, [174], [177], [184];

G. echinodiscus, G. spira, G. taenioides, [184]

Gills, of Polychaeta, [252], [265], [268] f.;

of Arenicola, [333];

of Chlorhaemidae, [334];

of Cirratulus, [326];

of Euphrosyne, [265], [318];

of Eunicidae, [318];

of Nereis, [246];

of Sabelliformia, [260], [261];

development of, [275];

of Sabella, [286];

colour of, [294];

of Sabellaria, [263];

of Serpulidae, [261];

of Sternaspis, [336];

of Sigalionina, [313];

of Terebellidae, [329];

of Oligochaeta, [352], [353];

of Leeches, [395];

of Gephyrea, [416]

Gizzard, in Rotifers, [199], [210];

in Polychaeta, [271], [307];

in Oligochaeta, [358];

in Polyzoa, [477], [480], [532] f.

Glands, on parapodia, [249];

of Phyllodocids, [314];

oesophageal, [271], [272], [358];

tube-forming, [287], [304], [327]

Gland shields, [287], [304], [306];

of Sabellids, [337];

of Terebellids, [327]

Glandular papillae, of Polygordius, [244]

Glossiphonia (= Clepsine), [393], [396], [399], [404], [407];

anatomy, [397], [398], [401];

spermatophore, [402]

Glossiphoniidae, [406]

Glycera, cirrus, [265];

habitat, [286];

jaws, [270];

nephridium, [254];

parapodium, [264];

prostomium, [259];

tentacles, [262];

G. capitata, distribution, [299];

G. meckelii, [320]

Glyceridae, [258], [320];

gills, [268];

coelomic corpuscles, [253]

Glyphidrilus, [386]

Gnathobdellae, [396] f., [407]

Gnathobdellidae, [407]

Gnathosyllis, colour of, [293]

Gobio, parasites of, [182], [183]

Golfingia, [426], [428], [430]

Goniada, [320]

Goodrich, on Oligochaeta, [378]

Gordiidae, [123], [164] f.

Gordiodrilus, [383] f.

Gordius, [164] f., [164];

G. tolosanus, [165] f., [170]

Gosse, on Rotifers, [198], [209] n., [220]

Gossea, [232], [235]

Goujon, on Trichina, [146]

Gourret, on Chaetognatha, [187]

Graff, von, on Rhabdocoelida, [44];

on Geonemertes, [101], [117]

Graffilla, [50];

occurrence, [45]

Grassi, on Cestoda, [80] n., [89];

on Chaetognatha, [190], [193]

Grater, of Eunicidae, [270]

Greef, on Echiuroidea, [441], [444]

Gregarines, in Polychaeta, [299];

in Gephyrea, [444]

Gregory, on Polyzoa, [519], [520]

Grinder, of Eunicidae, [270]

Grube, on Oligochaeta, [347], [352];

on Hirudinea, [395]

Grubea, [308];

attachment of eggs, [275]

Guanin, in coelomic corpuscles, [253]

Guinea-worm, [147]

Gunda, [31], [41], [42]

Gundidae, [42]

Gymnolaemata, [476], [512], [518];

lophophore, [476];

in fresh water, [492]

Gyrator hermaphroditus, [49]

Gyrocotyle (= Amphiptyches), [91];

G. rugosa, [77];

G. urna, [77]

Gyrodactylidae, [53], [61], [73]

Gyrodactylinae, [73]

Gyrodactylus, [55], [61], [73]

Haberlandt, on Convoluta, [43]

Habits, of Platyhelminthes, [3], [7], [21], [35], [43];

of Nemertinea, [114];

of Gordiidae, [170] f.;

of Chaetognatha, [189];

of Rotifers, [206], [226];

of Gastrotricha, [232], [234], [235];

of Polychaeta, [285];

of Oligochaeta, [366];

of Gephyrea, [426], [433], [442];

of Phoronis, [451]

Haemadipsa, [408];

eye, [394]

Haemal fluid, [252]

Haematocleptes, parasitic, [297]

Haementeria, [407]

Haemerythrin, [416];

in Magelona, [252]

Haemoglobin, in Nemertinea, [107], [108];

in Chaetopoda, [252], [253], [291], [356];

in Gephyrea, [437];

in Phoronis, [456]

Haemopis, [393], [407]

Halicryptus, [432], [433];

anatomy, [430]

Hallez, on Turbellaria, [7], [21], [40]

Halosydna, [298]

Hamann, on Nematoda, [131], [133], [136] n.;

on Acanthocephala, [176], [180]

Hamingia, [435] f., [442];

males of, [438]

Haplobranchus, [339];

gills, [261]

Haplodiscus, [43], [49]

Haplodrili, [241]

Hares, parasites of, [141], [145]

Harker, on Oligochaeta, [369]

Harmer, on Polyzoa, [465] f.

Harris, on Rotifera, [197]

Hartog, on Rotifera, [197] f.;

on Gastrotricha, [231] f.;

on Kinorhyncha, [236] f.

Haswell, on Temnocephalidae, [53];

on Phoronis, [451]

Hatschek, on affinities of Polyclads, [28] n.;

on nature of Cestodes, [76];

on Trochophore, [229];

on development of Gephyrea, [419], [447]

Head, of Nereis, [246], [248];

of Polychaeta, [259] f.;

regeneration of, [283];

of Tomopteris, [315];

of Aphrodite, [260];

of Chlorhaemidae, [334];

of Eunice, [262];

of Nephthys, [262];

of Phyllodoce, [262];

of Polydora, [261];

of Polynoid, [262];

of Sabella, [261];

of Sabellaria, [263];

of Syllid, [262];

of Trophonia, [262]

Hedruris, [163]

Hekaterobranchus, [326]

Heliodrilus, [359], [380]

Heliopora, containing Polydora, [298]

Heller, on human parasites, [139]

Hemichordata, [462]

Hemilepidia, colour of, [292]

Hemistomum, [73]

Hemitubifex, [378]

Henlea, [369]

Hermadion, [299]

Hermaphrodite, Nemertinea, [109];

Polychaeta, [273] f.

Hermellidae, [258], [341]

Hermelliformia, [258], [306], [341]

Hermione, [312];

chaetae, [266], [267]

Hermionina, [309], [311]

Herpobdellidae, [407]

Hertwig, O., on Chaetognatha, [187] n.

Hesionidae, [258], [308];

segments, [258];

head, [263];

swim-bladder, [272];

genital organs, [274];

parasitic, [297]

Hesperodrilus, [352] f., [369], [378] f.

Hesse, on nervous system of Nematoda, [127]

Heterakis, [131], [139]

Heterocotylea, [73]

Heterodera, [155], [160], [164]

Heterogamy, [66] n.

Heteronemertini, [113]

Heteronereid phase, [276] f.;

chaetae, [246], [276];

parapodia, [276], [277]

Heteronereis, [276], [281]—see Heteronereid

Heteropora, [520] n.

Heterosyllis, [278], [279], [281]

Hexacotyle, [73]

Hexarthra, [223], [226]

Hibernaculum, [501], [502]

Hincks, on Polyzoa, [475], [500], [508], [516], [519], [523]

Hippothoa, [528]

Hippuraria, [533]

Hirudinea, [241], [392] f.;

external characters, [392];

British species, [393];

eyes, [395];

branchiae, [395];

alimentary canal, [396];

vascular system, [396];

body-cavity, [397];

nephridia, [399];

reproductive organs, [401];

cocoons, [404];

classification, [405]

Hirudiniculture, [393]

Hirudo, [393], [396] f., [399], [403], [405], [407];

nephridium, [400]

Hislopia, [492]

Histioderma, [302]

Histriobdella, [242] n.

Histriodrilus, [242] n.

Holloway, on Rotifers, [227]

Holomyarii, [137]

Holostomatidae, [63], [64], [73]

Holostomum, [73];

H. excavatum, [63]

Holothurian, as host, [298]

Homalogaster, [73]

Hood, of Sabellaria, [263], [306]

Hooks, of Trematodes, [53], [56], [57];

of Cestodes, [75], [85];

of Cestode-larvae, [87], [88];

taxonomic value in Cestodes, [90] f.

Hoplonemertea, [106], [109], [110];

auditory organs, [106], [110];

British species, [110];

characters, [110];

development, [113];

proboscis, [110]

Hornera, [518], [532]

Horse, parasites of, [68], [83], [90], [125], [140], [142], [163]

Horse-leeches, [393] f.

Horst, on Oligochaeta, [354]

Hubrecht on Nemertinea, affinities, [120];

classification, [109];

excretory system, [108];

nervous system, [105]

Hudson, on Rotifera, [197], [198], [215] n., [220] n., [223] n., [228]

Hudsonella, [224]

Huxley, on Rotifers, [198], [229];

on Polychaeta, [246];

on Molluscoidea, [475]

Huxleya, [525], [527]

Hyalinoecia, [299], [318], [319];

tentacles, [262];

composition of tube of, [290]

Hydatina, [199], [200], [202], [204], [213], [224], [226], [228]

Hydatinidae, [224]

Hymenolepis, [91];

generic characters, [91];

H. diminuta (= Taenia flavopunctata), life-history, [83];

specific characters, [91];

H. murina (= Taenia murina), [70];

life-history, [83], [89], [91];

H. nana, [80];

life-history, [83];

specific characters, [91]

Hyocrinus, as host, [342]

Hyperiodrilus, [363] f.;

reproductive organs, [363]

Hypodermic impregnation, [27], [218]

Hypodermis (= Epidermis) of Gordius, [165];

of Rotifera, etc., [205], [232]

Hypophorella, [478], [518], [533];

larva, [510]

Hyporhynchus, [49]

Hystrichis, [147], [149], [163]

Ichthydium, [235]

Ichthyobdellidae, [406]

Ichthyonema, [131], [147], [149], [163]

Ichthyotaenia, [91]

Ichthyotaeninae, [85], [91]

Idmonea, [518], [532]

Iguana, parasites of, [142]

Iijima, on yolk-glands, [38] n.

Illoricata, [223]

Ilyodrilus, [378];

chaeta, [350]

Ilyogenia, [388]

Imogine, [19]

Inarticulata, [517], [518]

Incudate, [210], [211]

Incus, in Rotifers, [210]

Inermia, [445]

Infusoriform embryos, [93]

Insects, parasites of, [142], [150], [152], [153], [154], [160], [163], [179], [183], [184], [185]

Internal sac, [509], [511]

Internode, [525]

Interproglottidal glands, [90]

Intertentacular organ, [469], [473], [508]

Introvert, in Polychaeta, [249], [250];

in Gephyrea, [412], [424]

Investing membrane, in ectoparasitic Trematodes, [57];

in Cestodes, [85]

Ioda, form of head, [278]

Isacis, [163]

Jammes, on skin of Nematoda, [126]

Jaws, of Nereis, [248], [250], [270];

of Polychaeta, [269] f.;

of Eunicidae, [270];

of Polynoid, [270];

of Autolytus, [270];

fossil, [302];

of Glycera, [270]

Jelly, Miss, on Polyzoa, [523]

Jensenia, [50]

Jimenez, on Leeches, [407]

Joblot, on Rotifers, [197]

Johnston, on Hirudinea, [393]

Joliet, on development of Rotifers, [218];

on Polyzoa, [508]

Jungermanniaceae, inhabited by Rotifers, [227]

Jurassic, Serpulids, [301];

Polyzoa, [520] f.

Kaiser, on Acanthocephala, [177]

Kamptoderm, [469], [470]

Keferstein, on Polycladida, [7], [10]

Kennel, von, on Nemertinea, [108];

on Malacobdella, [101] n., [119]

Kerria, [384]

Kinorhyncha, [236] f.

Kleinenberg, on Trochophore, [229]

Koellikeria, [73]

Kölliker, on Distomum okenii, [71]

Koren and Danielssen, on Gephyrea, [442], [443]

Kowalevsky, on Hirudinea, [397];

on Phoronis, [458]

Kraepelin, on Polyzoa, [493], [502]

Krause, on parasites, [163]

Krohn, on Nemertine development, [99]

Krohnia, [186];

species, [192], [194];

American species, [534]

Krukenberg, on haemerythrin, [416]

Kynotus, [386]

Labrorostratus, [297]

Lacinularia, [200], [213], [215], [221], [226]

Lacrymaria, [235]

Laetmonice, [312]

Lagenipora, [528]

Lamarck, on Gephyrea, [411]

Land, Planarians, [4], [30], [33], [34], [36];

Nemertines, [101], [117];

Oligochaeta, [347] f.;

Leeches, [408]

Lang, on Polyclads, [7], [17], [21] f., [27], [28] n.;

on nature of Cestodes, [76]

Lanice, [328];

Hypophorella in tubes of, [478], [533]

Lankester, on Trochosphere, [229];

on Earthworms, [347];

on Hirudinea, [397];

on Gephyrea, [430], [437], [439];

on Podaxonia, [461]

Larva, Müller's, [29];

of Polystomum, [59];

of Diplozoon, [60];

of Gyrodactylus, [61];

of Holostomatidae, [63], [64];

of Distomum [64], [65], [67];

hosts of larvae of digenetic Trematodes, [71] f.;

of Calliobothrium, [77];

of Cestodes, [79] f.;

table of Cestode larvae, [83], [85], [87];

of Schistocephalus, [84];

of Bothriocephalus, [87];

of Dipylidium (Cysticercoid), [83], [88] f.;

of Mesozoa, [92], [93];

of Nemertinea, [113];

Trochosphere, [229], [274], [439], [510];

of Polygordius, [245];

of Polychaeta, [274], [275];

of Chaetopterus, [325];

of Myzostoma, [344];

of Gephyrea, [419], [439];

of Phoronis, [458];

of Polyzoa, [466], [509], [511], [520]

Lateral organs, of Capitellidae, [343]—see also Ciliated pits

Laurer's Canal (= Laurer-Stieda canal), [57], [87]

Leaena, [300], [327] n.

Lecanocephalus, [131], [133]

Leckenby, on Priapulus, [433]

Leeches, [241], [392] f.—see also Hirudinea

Leeuwenhoek, on Rotifera, [197]

Legrain, on Nematodes in deserts, [156]

Legros, on Trichina, [146]

Lehnert, on Bipalium, [36], [37]

Leidy, on Rotifers, [198]

Leimacopsis, [37], [42]

Lemnisci, [176]

Lepas, as host, [298]

Lepidasthenia, [293], [311]

Lepidoderma, [235]

Lepidonotus (subgenus of Polynoe), eye, [255]

Lepralia, [516], [518], [528], [530], [531] n.;

L. foliacea, [478], [527];

larva, [511]

Leprea, [328]

Leptodera, [129], [131], [133], [160]

Leptoplana, [7], [8], [9], [11], [14], [17];

British species, [19];

habits, [8] f.;

anatomy, [11] f.

Leptoplanidae, [19]

Leptostoma, [396]

Lesson, on Polyclads, [24]

Leuciscus, parasites of, [173], [182]

Leuckart, on Platyhelminthes, [6], [64] f., [70], [76];

on Nemertinea, [99];

on Nematoda, [136], [139], [140], [142], [146], [163];

on Hirudinea, [395]

Leucochloridium, [65], [66]

Leucocytes, of Polychaeta, [252]

Leucodore—see Polydora

Leydig, on Rotifers, [198]

Lias, Serpulids in, [301]

Libyodrilus, [364], [385], [386]

Lichenopora, [518], [531]

Life-history, of Trematodes, [4];

of Polystomatidae (Polystomum, Diplozoon, Gyrodactylus), [58] f.;

of digenetic Trematodes, [63] f.;

table of, [71];

of Cestodes, [5] f., [87];

table of life-histories of Cestodes, [83];

of Dipylidium, [88];

of Dicyemidae, [93];

of Nematoda, [159];

of Gordius, [170];

of Acanthocephala, [179]—see also Development

Ligula, [91];

occurrence, [85]

Ligulinae, [91]

Lim Boon Keng, on Earthworms, [349]

Lima, nests of, [298]

Lime, secreted by Serpulidae, [290]

Limnaea truncatula, host of larvae of Distomum hepaticum, [67], [72]

Limnatis, [407]

Limnias, [205], [221];

early description of, [197]

Limnodrilus, [378]

Lineus, [111];

L. marinus (= L. longissimus), [99], [100], [111], [114];

Borlase on, [99];

size of, [100];

L. gesserensis (= L. obscurus = L. sanguineus), recuperative powers of, [116]

Linguatulida, affinities of, [344]

Linnaeus, on Cestodes, [78];

on Gephyrea, [411];

on Polyzoa, [474]

Linstow, von, on classification of Nematodes, [137];

on life-history of Ascaris lumbricoides, [140];

on parasitism, [162];

on Gordius, [166], [171], [173]

Lip, lip-membrane, lip-processes, of Sabellidae, [261], [337]

Lipobranchius, [334];

shape of body, [259]

Lipochromes, in Polychaeta, [292]

Lister, on Polyzoa, [497]

Lithodomous, Polychaeta, [287]

Lithographic slate, fossil Polychaeta from, [301], [302]

Liver, -fluke, [51];

-rot, [68]

Locomotion, of Planarians, [9], [10], [36];

of Polyclads, [22] f.;

of Nemertinea, [114], [115];

of Chaetognatha, [190];

of Rotifers, etc., [206], [235];

of Dinophilus, [243];

of Phylactolaemata, [496]

Looss, on Trematoda, [62] n., [66], [70]

Lopadorhynchina, [314]

Lopadorhynchus, [314];

L. erythrophyllum, colour of, [292]

Lophochaeta, [351];

chaeta, [350]

Lophohelia, with Eunice, [298], [319]

Lophophore, in Phoronis, [453];

in Polyzoa, [476], [476], [495]

Lophopus, [494], [499], [504], [505], [518], [519];

movements, [496], [497];

fission, [496], [506];

statoblast, [502], [503]

Lorica, in Rotifers, [205]

Loricata, [205], [224]

Lota, parasites of, [182]

Loxosoma, [489] f., [489], [490], [506], [518];

on Polychaeta, [299], [489];

on other animals, [489];

buds, [489], [490], [506];

larva, [509]

Lug-worm, castings of, [285];

as bait, [297]

Lumbricaria, [302]

Lumbricidae, [362], [371] f., [388]

Lumbricobdella, [392]

Lumbriconereis, [318], [320];

from fresh water, [284]

Lumbriconereites (misprinted in text), [302]

Lumbriculidae, [350], [361], [379]

Lumbriculus, [379];

as host of Rotifer, [211] n.

Lumbricus, [349], [351], [356], [367], [368], [371], [389] f., [403] f.;

generative organs, [362];

cocoon, [365]

Lunulites, [518];

vibracula, [487]

Lurg, [317]

Lycoridae, [315]

Lysidice, [297], [320]

MacGillivray, on Polyzoa, [519]

M‘Intosh, on Nemertinea, [110] n., [115], [116];

on Phoronis, [454]

Macraspis, [73]

Macrobdella, [393], [406];

sense-body, [394]

Macrorhynchus, [44], [47];

British species, [49]

Macrostoma, [44], [47];

British species, [49]

Macrostomatidae, [49]

Magelona, [325];

haemerythrin in, [252]

Magelonidae, [258], [325]

Main-gut, of Leptoplana, [8], [13];

of Polyclads, [17]

Malacobdella, [101];

description of, [119];

M. grossa, [110], [119];

excretory system of, [108]

Malacocotylea (= Digenea), [73]

Maldanidae (= Clymenidae), [258], [332];

shields, [259];

anal funnel, [259];

chaetae, [266], [267], [268];

colour, [293]

Male, of Rotifers, [199], [200], [217], [223] n.;

of Echiuroids, [438]

Malleate, [210]

Malleoramate, [210], [211]

Malleus, [210]

Mammals, Trematodes of, [62], [63], [67]-70, [71] f.;

Cestodes of, [77]-84, [89]-91;

Nematodes of, [163];

Acanthocephala of, [183], [184]

Man, Trematode-parasites of, [63], [68]-70;

Cestodes of, [74], [78]-81, [83], [89] f.;

Nematodes of, [125], [139], [140], [143], [145], [147], [163];

Gordius of, [173];

Echinorhynchus of, [183]

Man, De, on free-living Nematodes, [157]

Manayunkia, [284], [339] n.

Mandible, of avicularium, [482], [524]

Manson, on Filaria, [149]

Manubrium, [210]

Marginal groove, of Leptoplana, [15]

Maricola, [30], [32], [42]

Marine, Rotifers, [226];

Oligochaeta, [366];

Leeches, [406]

Marphysa, [276], [319];

as bait, [297];

as host, [297]

Mastax, of Rotifers, [199], [210]

Masterman, on Chaetognatha, [190];

on Phoronis, [461]

Mastigocerca, [225]

Mastigophora, [518], [529];

vibraculum, [484]

Mastobranchus, gill of, [268], [331]

Matzdorf, on Leeches, [369]

Maupas, on Rotifers, [217]

Mbalolo, [297]

Meckelia asulcata, [111]

Mecynostoma, [49]

Median pore, in Cheilostomata, [484], [524]

Megadrili, [373], [374], [380] f.

Megalotrocha, [221]

Megapora, [530]

Megascolex, [351], [372], [381], [383]

Megascolides, [349], [358], [372], [382];

body-wall and nephridia, [357]

Mégnin, on parasites, [164]

Meissner, on Polyzoa, [493]

Melania, Coabangia in shell of, [284]

Melanin, [292]

Melicerta, [202], [205], [206], [210], [215], [218], [219], [221], [226];

early description of, [197]

Melicertaceae, [203], [221]

Melicertidae, [201], [203], [205], [211], [213], [221]

Melinna, [330]

Membranipora, [481], [492], [518], [519], [523], [528], [530];

phosphorescence, [478];

function of aperture, [500];

larva, [509], [510];

variation, [516]

Membraniporella, [518], [524], [528]

Menipea, [518], [526], [527]

Mermis, [131], [150], [160], [163]

Mermithidae, [150], [163]

Meromyarii, [129], [137], [142]

Mertens, on Polyclads, [6], [23]

Mesobdella, [407]

Mesocestoides, [91];

M. lineatus, life-history, [84];

specific characters, [90]

Mesonemertini, [112]

Mesostoma, [44], [45];

reproduction, [48];

British species, [49]

Mesostomatidae, [49]

Mesotrochal larva, [325]

Mesozoa, [92] f.

Metamerism, [249]

Metamorphosis, in Polycladida, [16], [28];

in Trematodes, [5], [66] f.;

in Cestodes, [5], [74], [76], [87]-89;

in Phoronis, [459];

in Polyzoa, [512]

Metanemertini, [112]

Metastatica (= Holostomatidae), [73];

life-histories, [64]

Metopidia, [200], [225]

Metschnikoff, on Orthonectida, [94];

on Nemertines, [99];

on Chaetosomatidae, [158]

Meyer, on Polychaeta, [261]

Michaelsen, on Earthworms, [349], [353], [359], [370] f., [375], [385]

Microchaeta, [362]

Microcodides, [224]

Microcodon, [202], [215], [224], [230]

Microcodonidae, [202], [220] n., [224]

Microcotyle, [73];

eggs of M. labracis, [58]

Microcotylinae, [73]

Microdrili, [373], [374] f.

Microplana, [34], [42]

Micropora, [518], [530];

zooecium, [523]

Microporella, [516], [518], [519], [529];

avicularia, [484], [485];

median pore, [501]

Microscolex, [372], [382], [383], [384]

Microstoma, [44];

asexual reproduction, [44];

sexual organs, [47];

British species, [49]

Microstomatidae, [49]

Micrura, [101], [114];

British species, [111]

Migrations, of Trematode-larvae, [5], [52], [63] f.;

of Cestode-larvae, [5], [74], [83], [87]

Millson, on Oligochaeta, [368], [387]

Millsonia, [382] f.

Milne-Edwards, on Polyzoa, [475]

Mimicry, in Polychaeta, [293] f.

Mimosella, [518], [532];

movement of zooecia, [481]

Molluscoidea, [475]

Molops, host of Gordius, [172]

Monhystera, [160]

Moniez, on Cestodes, [84] n., [85];

on Earthworms, [369]

Moniezia, [83], [91];

characters of genus, [90];

M. alba, M. benedeni, M. denticulata, [90];

M. expansa, [83], [90];

M. neumani, M. oblongiceps, M. planissima, M. trigonophora, [90]

Moniligaster, [359], [380], [402]

Moniligastridae, [361], [373], [380]

Monkey, parasites of, [145]

Monocotyle, [73]

Monocotylinae, [73]

Monogenea (Monogenetic Trematodes), [5], [53];

classification, [73]

Mononchus, [154]

Monoophorum striatum, [50]

Monopora vivipara, [117]

Monoporus rubropunctatus, [49];

reproductive organs of, [47]

Monostomatidae, [73]

Monostomum, [71], [73];

life-history, [72]

Monostyla, [225], [226]

Monotidae, [50]

Monotus, [36];

British species, [50];

M. fuscus, [45];

habits, [46]

Monozoa, [91]

Montgomery, on Stichostemma eilhardii, [118]

Monura, [225]

Morren, on Earthworms, [347]

Moseley, on Land Planarians, [7], [35] n., [37];

on Pelagonemertes, [101], [114]

Movements, in Rotifers, etc., [206], [235]

Moxon, on Rotifers, [198]

Mucro, [522], [525]

Mucronella, [518], [522], [528], [529], [530], [531]

Müller, F., on Triclads, [37];

on Polyzoa, [493]

Müller, O. F., on Turbellaria, [6];

on Rotifers, [197];

on Oligochaeta, [348], [352]

Müller's larva, [16], [28], [29]

Muscles, of Leptoplana, [12];

of intestine in Polyclads, [24];

of Nemertinea, [102], [103];

of Nematoda, [128];

of Gordiidae, [165];

of Chaetognatha, [187];

of Rotifers, etc., [206], [233], [237];

of Nereis, [247], [249] f.;

of Polyzoa, [469], [470], [472], [499], [500]—see also Body-wall

Musculo-glandular organ, in Triclads, [39], [40]

Myrianida, [280], [308];

gemmiparity, [279], [280];

markings, [293]

Myrianites, [302]

Mytilia, [225], [226]

Myxicola, [338];

tori uncinigeri, [268];

eyes, [272];

otocyst, [273];

tube, [285];

supposed mimicry, [294]

Myzostoma, anatomy, [342] f.;

M. cirriferum, [343];

M. glabrum, [342]

Myzostomaria, [241];

structure and affinities, [342] f.

Myzostomatidae, [342]

Naidomorpha (= Naididae and Naids), [348], [352], [375] f., [377], [378], [400];

chaetae, [350], [367];

reproductive organs, [361];

asexual reproduction, [281], [377]

Nais, [348], [377];

chaetae, [350]

Nannodrilus, [382] f.

Natatory chaetae, of Nereidae, [277];

of Syllidae, [278], [307]

Nathusius, on parasites, [63], [163]

Nauphanta, [314], [315]

Nebalia, Rotifers parasitic on, [225]

Nectochaeta, [291]

Nectonema agile, [164], [168], [169], [173]

Nemathelminthes, [123] f., [168]

Nematobothrium, [4], [55], [71], [73]

Nematoda, [123];

anatomy, [124] f.;

embryology, [135];

classification, [136];

life-history of, [159] f.

Nematogen, [94];

Secondary Nematogen, [94]

Nematomorpha, [123], [164] f.

Nematoxys, [139], [142], [161], [163]

Nematozoa, [137]

Nemertes, British species, [110];

deposition of ova and spermatozoa in, [116]

Nemertinea, affinities, [119];

anatomy, [102];

body-wall, [102];

breeding, [116];

cephalic slits and cerebral organs, [107], [273];

circulatory system, [106], [107];

classification, [109] f.;

colour, [102];

contractility, [102];

development, [113];

diagram, [104];

digestive system, [103];

excretory system, [108], [108];

external characters, [101];

food, [115];

fresh-water forms, [101], [118];

generative organs, [109];

geographical distribution, [117];

habitat, [100];

habits, [114];

land forms, [101], [117];

locomotion, [114], [115];

nervous system, [105], [106];

parasitic forms, [101], [119];

pelagic forms, [101], [114];

proboscis, [100], [101] f., [103], [104], [110], [115];

regeneration, [115];

sense organs, [101], [106], [107];

size, [100]

Nemertodrilus, [360]

Nemertoscolex, [444]

Neodrilus, [384]

Neorhynchidae, [184]

Neorhynchus clavaeceps, [178], [181], [184];

N. agilis, [184]

Nephelis, [392] f., [397], [399], [401], [403], [405]

Nephridium, of Archiannelida, [243], [244];

of Nereis, [253];

of Arenicola, [253], [254];

of Polychaeta, [253];

dimorphism of, in Polychaeta, [269];

thoracic, of Sabelliformia, [306];

of Terebellidae, [327];

of Chlorhaemidae, [334];

of Myzostoma, [344];

of Oligochaeta, [356] f., [381] f., [400];

of Leeches, [399];

of Gephyrea—see Brown tubes;

of Phoronis, [456]

Nephthydidae, [258], [317]

Nephthys, [317];

nephridium, [254];

prostomium, [259], [260];

head, [262];

tentacles, [262];

peristomium, [263];

parapodium, [264], [265];

cirrus, [265];

gill, [268];

jaws, [270];

habitat, [286];

as bait, [297]

Nereidae, [258], [315];

palps, [260];

colour, [292]

Nereidiformia, [258], [303];

vascular system, [252];

anal cirri, [259];

prostomium, [259], [260];

tentacles, [262];

peristomial cirri, [263];

parapodium, [264] f.;

cirri, [265];

chaetae, [266];

jaws, [269];

eyes, [272];

ciliated organ, [273];

regeneration in, [283];

food, [296];

fossil, [301] f.

Nereilepas, [317]

Nereis, [246], [299], [301], [316] f.;

anatomy, [245] f., [247] f.;

transverse section, [247];

parapodium, [246], [247], [265], [317];

chaetae, [246];

head, [246], [248], [316];

alimentary canal, [249] f., [251];

jaws, [248], [250], [270], [316];

nervous system, [254], [255];

eye, [255];

vascular system, [247], [251];

dorsal ciliated organ, [247], [254], [256];

nephridium, [253];

reproduction, [256];

sexually mature, [276], [276] f.;

sexual dimorphism and Heteroneid phase, [276] f.;

epitokous (= epigamous) and atokous phase, [277] n.;

from fresh water, [284];

burrow, [286];

pigment, [292];

as bait, [297];

commensalism, [298];

as host, [299];

British species, [316] f.

Nereites, [302]

Nerine, [299], [322];

habitat, [286];

N. vulgaris, head, [322]

Nerve plexus of Nemertinea, [103], [105]

Nervous system, of Leptoplana, [13], [14];

of Polyclads, [26], [30];

of Planaria lactea, [39];

reduced in parasitic Rhabdocoels, [45];

of Temnocephala, [54];

of Polystomatidae, [56];

of Cestodes, [75], [86];

of Nemertinea, [105], [106];

of Nematoda, [127];

of Gordiidae, [166];

of Acanthocephala, [177];

of Chaetognatha, [187];

of Rotifera, etc., [215], [234], [237];

of Archiannelida, [243], [244];

of Polychaeta, [254];

visceral, of Polychaeta, [255];

of Oligochaeta, [353], [374];

of Gephyrea, [416], [431], [437], [440], [445];

of Phoronis, [456];

of Polyzoa, [471]

Neumann, on parasites, [164]

Neuropodium, [246], [247], [264], [266], [268]

Newton, on zoo-geographical regions, [372]

Nicolea, [328];

gill, [329]

Nicomache, [332];

tail, [332];

tube, [287];

N. lumbricalis, colour, [292];

distribution, [299]

Nitsche, on Polyzoa, [475] n., [478], [500]

Nitzschia, [56], [73]

Norman, on Polyzoa, [475]

Norodonia, [492]

Notamia, [518], [526]

Noteus, [225]

Notholca, [225], [226]

Notocotyle, [73]

Notomastus, [331];

chaetae, [268]

Notommata, [217], [224], [226]

Notommatidae, [200], [205], [207], [215], [223], [224]

Notophyllum, colour, [293]

Notopodium, [246], [247], [264], [265], [268]

Notops, [200], [224]

Notopygos, [259]

Nuchal cirri of Eunicidae, [318];

Nuchal organ—see Ciliated pits

Ocnerodrilus, [383]

Octobothrium, [56], [73]

Octochaetus, [358], [384]

Octocotylinae, [73]

Octotrocha, [221]

Odontosyllis, reproduction of, [278];

as host, [297].

Oecistes, [205], [206], [221]

Oenonites, [302]

Oesophageal glands, [271], [358]

Ogmogaster, [73]

Oka, on Hirudinea, [399] f.;

on Polyzoa, [500]

Olfactory pits, in Polyclads, [26];

in Triclads, [36]

Oligocelis, [42]

Oligochaeta, [241], [347] f.;

external characters, [348];

body-wall, [349];

chaetae, [350], [351];

branchiae, [352];

nervous system, [353];

sense-organs, [354];

coelom and vascular system, [355];

excretory organs, [356];

alimentary canal, [358];

reproductive organs, [360];

habitat, [365];

phosphorescence, [368];

distribution, [369];

classification, [373];

Rotifers parasitic on, [227]

Oligocladus, [19], [22]

Oligognathus, [297]

Ollulanus, [142];

O. tricuspis, [144], [161]

Omalostoma, [49]

Onchnesoma, [422], [423], [426], [430], [447]

Onchocotyle, [73]

Oncholaimus, [157]

Onchosphaera-larva of Cestodes, [87], [88]

Onuphin, [290]

Onuphis, [290], [318], [319];

O. conchylega, tube, [287]

Onychochaeta, [388];

chaeta, [351]

Onyx, [131]

Ootype, in Polystomum, [59].

Operculum, of Serpulidae, [261], [276], [339];

of Spirorbis, as brood-pouch, [261], [276];

of Cheilostomata, [466], [477], [481], [482], [522], [524]

Opesia, [524]

Ophelia, [299], [332];

eggs, [275];

coelomic corpuscles, [252]

Opheliidae, [258], [331];

gill, [265];

ciliated pits, [272]

Ophiodromus, [308];

O. flexuosus, parasitic, [297]

Ophryotrocha, [310], [320];

pelagic, [291];

genital organs, [274]

Opisthotrema, [73]

Opistoma, [50]

Orbigny, D', on Polyzoa, [519], [520]

Orifice, of zooecium, [466], [469], [470], [524];

secondary, [522], [524]

Örley, on classification of Nematodes, [137]

Orthonectidae, [13], [92], [94] f.

Otocyst (and Otolith), of Turbellaria, [26];

of Nemertinea, [106], [110];

of Polychaeta, [273]

Otomesostoma, [46], [49]

Otoplana, [50]

Oudemans, on Nemertinea, [108]

Ovary (and Oviduct), of Leptoplana, [11], [14], [16];

of Polyclads, [27];

of Planaria, [38], [39];

of Rhabdocoelida, [47];

of Temnocephala, [54];

of Polystomatidae, [57];

of Diplozoon, [60];

of Gyrodactylus, [61];

of Distomum macrostomum, [65];

of Calliobothrium, [75];

of Archigetes, [76];

of Schistocephalus, [86];

of Rhopalura, [95];

of Myzostoma, [343]—see also Reproductive organs

Ovicell, in Cheilostomata, [466], [466], [468], [481], [482], [484], [522] f., [525];

in Cyclostomata, [479], [480], [521], [525]

Oviduct—see Ovary

Owenia, [325]

Ox, parasites of, [79], [83], [125], [139], [140], [143]

Oxysoma, [139], [142]

Oxyuris, [129], [131], [135], [139], [141], [160];

O. ambigua, [141];

O. curvula, [141], [163];

O. diesingi, [141], [142];

O. vermicularis, [141], [163];

O. blattae, O. blatticola, O. hydrophili, O. megatyphlon, O. spirotheca, [142]

Paddle worm, [313]

Paedogenesis, [151]

Pagenstecher, on Nemertinea, [99]

Palaemonetes, host of Nectonema, [174]

Palaeonemertea, [109], [112];

characters, [111];

development, [113]

Palaeozoic, Serpulidae, [301];

Eunicidae, [302];

Polyzoa, [520]

Paleae, of Sabellaria, [267]

Palmicellaria, [527], [528]

Palolo viridis, as food, [297]

Palps, of Nereis, [248], [255];

nerves to, [254];

of Polychaeta, [260] f.;

development of, in Sabelliformia, [275];

of Hermelliformia, [306];

of Syllidae, [307]

Paludicella, [492], [494], [501], [502], [505], [518]

Paludicola, [30], [42]

Panthalis, [313]

Paragnaths, [248], [250], [316]

Parapodium, of Nereis, [246], [247];

of Polychaeta, [264] f.;

of Heteronereid, [276], [277];

muscles of, [247];

glands of, [249], [314];

of Myzostoma, [342]

Paraseison, [212], [225], [226]

Parasitic, Turbellaria, [51];

Polyclads, [22];

Triclads, [32];

Rhabdocoela, [45], [51];

Nemertinea, [101], [119];

Rotifers, [204], [227];

Polychaeta, [297];

Leeches, [406]

Parasitism, effect on the parasite, [161], [177];

effects on the host, [162]

Parenchyma, in Leptoplana, [11], [12];

of Müller's larva, [29];

in Triclads, [41];

in Acoela, [42];

in Cestodes, [85], [86]

Parovaria, of Phagocata, [38] n.

Parthenogenesis, amongst Rotifers, [200]

Pectinaria, [330];

body, [259];

tube, [285], [287];

P. auricoma, tube, [288];

P. belgica, [330]

Pectinatella, [496], [497], [505], [512], [518];

statoblast, [502]

Pedalion, [200], [201], [206], [211], [216], [223], [224], [225], [228], [230]

Pedalionidae, [223]

Pedetes, [224]

Pedicellina, [487], [488], [490], [506], [507], [518];

larva, [510], [513];

budding, [514];

on Polychaeta, [299]

Pelagic, Nemertinea, [101], [114];

Chaetognatha, [189]; Rotifera, [226];

Polychaeta, [291], [294], [314];

larvae of Polychaeta, [300], of Polyzoa, [520]

Pelagobia, [314]

Pelagonemertes, [101], [114]

Pelodera, [129], [131], [133]

Pelodrilus, [369], [377]

Pelodytes, [134]

Penis, of Leptoplana, [14], [15];

of Polyclads, [27];

of Planaria, [38], [39];

of Rhabdocoelida, [47];

of Temnocephala, [54];

of Calliobothrium, [75];

of Schistocephalus (cirrus-sac), [86]

Pennant, on Hirudinea, [406] n.

Pereyaslawzewa, on Acoela, [44] n.

Pergens, on Polyzoa, [500]

Perichaeta, [351], [357], [358], [372], [381], [381] f., [388], [394], [403]

Perichaetidae, [357], [362], [380]

Perienteric, blood-sinus, [252]

Perionyx, [381]

Perissogaster, [383]

Peristome, [481], [482], [522], [524]

Peristomial (tentacular) cirri, of Nereis, [248];

of Polychaeta, [263];

nerves to, [254]

Peristomium, of Nereis, [248];

of Polychaeta, [263];

of Sabellidae, [336]

Perrier, on Oligochaeta, [367], [385]

Petalostoma, [422], [426], [430], [447]

Petromyzon, host of Gordius, [173]

Petta, intestine of, [271]

Phagocata, [31], [32]

Phalacrophorus, [314]

Phanerocephala, [258], [303]

Pharynx, [4];

of Leptoplana, [8], [9], [12], [14];

of Polyclads, [17], [24];

of Discocelis, [23];

development of, in Polyclads, [29], [30];

of Triclads, [31], [37], [39];

of Temnocephala, [53], [54];

of Polystomatidae, [56];

of Digenea, [62], [64];

of Nereis, [249], [250], [251];

of Polychaeta, [269]

Phascolion, [423], [425], [428]

Phascolosoma, [416], [420], [423], [425], [428], [447];

as host of Loxosoma, [489]

Philippi, on Hirudinea, [406]

Philodina, [208], [222], [227]

Philodinidae, [222]

Phoronis, [450] f., [451], [452], [453], [455];

habits, [451];

anatomy, [453] f., [457];

development, [458], [458];

species, [460];

affinities, [461], [512]

Phosphorescence (and light-producing organs), in Rotifers, [226];

in Polychaeta, [272], [295], [296];

in Oligochaeta, [368];

in Polyzoa, [478]

Photodrilus, [368], [383]

Photogen (light-producing organ), of Polyophthalmus, [272];

of Tomopteris, [296], [315]

Phreodrilus, [369], [379]

Phreoryctes, [367], [377]

Phreoryctidae, [376]

Phylactella, [528], [530]

Phylactolaemata, [476], [493] f., [518];

lophophore, [476], [495];

occurrence, [493];

movements, [494], [496] f.;

reproduction, [501], [506], [507];

larva, [511], [512];

distribution, [493], [504];

affinities, [512]

Phyllacanthinae, [91]

Phyllobothrinae, [91]

Phyllobothrium, [76] n., [91]

Phyllocotyle, [73]

Phyllodoce, [313], [314];

head, [262], [263]:

eggs, [275], [314] n.;

colours, [291], [292];

parapodium, [264];

chaeta, [267]

Phyllodocidae, [258], [313];

parapodial cirri, [266];

as food, [297];

eggs, [314];

colours, [292], [293]

Phyllodocites, [302]

Phyllonella, [73]

Phymosoma, [413], [420], [421], [423] f., [425], [426]

Physaloptera, [163]

Pig, parasites of, [68], [79], [139], [147], [184]

Pigments, of Polychaeta, [291] f.;

of Gephyrea, [435]

Pike, Trematode of, [62];

Cestode of, [81], [84]

Pilidium larva, [113], [113], [229], [230]

Pionosyllis, [308]

Piscicola, [393], [406]

Pista, [328];

gill of, [329]

Pits, ciliated, of Polychaeta, [272], [273]

Placostegus, colour, [292];

from deep sea, [300]

Placunella, [73]

Plagiochaeta, [358], [381], [384]

Plagiostoma, [46];

British species, [50]

Plagiostomatidae, [50]

Planaria, [30], [31] f., [39];

British species, [42]

Planarians, [3], [7];

Dinophilus, compared with, [242], [243]

Planariidae, [42]

Planctoplana, [19]

Plankton, Rotifers in, [225]

Planocera, [18], [19], [20]

Planoceridae, [19], [23]

Planorbis, host of Gordius, [173]

Plants, parasites on, [154], [155], [157], [160]

Plasmodium, nature of, in Orthonectids, [94]

Plate, on Rotifers, [198], [225] n.

Platyaspis, [73]

Platycotyle, [73]

Platyhelminthes, [3] f.;

Nemertinea classed with, [119]

Plectanocotyle, [73]

Plectus, [160]

Pleionogaster, [381]

Plerocercoid larva, [84]

Plessis, du, on Tetrastemma lacustre, [101] n., [118]

Pleurocotyle, [73]

Pleurotrocha, [224], [226]

Ploesoma, [212], [225]

Ploima, [202], [203], [212], [213], [216], [220], [223], [226], [227]

Plumatella, [493], [494], [499], [503]-505, [518], [519];

protrusion of polypides, [499];

statoblasts, [499], [502], [503];

larva, [512]

Podal membrane, of Spionidae, [322]

Podaxonia, [461]

Polyarthra, [201], [224], [226]

Polybostrichus, [280]

Polycelis, [30], [31], [40], [42]

Polychaeta, [241], [245] f.;

classification, [257], [258], [303] f,;

head, [248], [259] f.;

parapodium, [246], [264] f.;

chaetae, [246], [266] f.;

coelomic fluid, [252];

nervous system, [254];

sense-organs, [255], [272];

ciliated pits, [272];

alimentary canal, with pharynx, [249], [250], [251], [269], [270], [271];

oesophageal glands, [271] f.;

nephridium, [253], [254], [269], [274];

genital duct, [254], [269];

genital cells, [256], [273] f.;

hermaphrodite, [273];

regeneration, [278], [282];

habits, [285];

carnivorous, [304];

distribution, [299];

from fresh water, [284];

from deep sea, [300];

pelagic, [291], [314];

boring, [287];

tubes, [287];

pigments, [291];

colours, [291] f.;

warning colours, [294];

protective devices and mimicry, [293];

phosphorescent, [295];

food of, [296], [299];

as bait, [296], [297];

as food for man, [297];

commensalism, [297] f.;

parasitic, [297] f.;

as hosts, [299];

extinct, [301], [302];

larva, [274], [276], [300];

provisional chaetae, [274]

Polychoerus, [49];

development of, [44] n.

Polycirrus, [330];

habits of, [285];

P. aurantiacus, warning colours, [294];

phosphorescence, [295];

P. haematodes, coelomic corpuscles, [253]

Polycladida (Polyclads), [4] f., [7];

classification, [16] f.;

development, [28] f.;

British species, [19], [20], [22]

Polycladus, [42]

Polycotyle, [73]

Polydora (= Leucodore), [323];

frontal ridge, [260];

head, [261];

special chaetae, [267];

with Heliopora, [298];

P. ciliata, borings, [287]

Polydoridae, [258], [323]

Polygordius, [242], [244];

development, [245]

Polymnia, [328]

Polymorphism, of Nereis, [277]

Polymyarii, [137], [142]

Polynoe [310];

segments [258];

parapodium, [265];

jaws, [270];

anus, [259];

nephridium, [254];

habits, [286];

as ectoparasites or commensals, [294], [298], [325];

distribution, [299], [300];

British species, [299], [310] f.;

P. squamata, [309];

elytron, [310];

P. clava, elytron, [310];

P. imbricata, elytron, [311]

Polynoina (= Polynoids), [309];

head, [262];

chaetae, [266], [267];

jaw, [270];

intestine, [271]; eggs, [275];

sexual dimorphism, [276] n.;

tubes, [285];

colours, [291], [292];

protective resemblance, [294];

phosphorescence, [295], [296];

food, [296];

parasitic and commensal, [297], [325];

elytra, [275], [294], [295], [299], [309] f.

Polyodontes, [313] n.

Polyophthalmus, [332];

segmental eyes, [272], [296];

otocyst, [273]

Polype à pannache, [496]

Polypide, [468], [469], [474], [488], [523];

retraction and protrusion, [498] f.

Polypide-bud, [468], [472], [487], [496], [499], [501], [510];

connected with reproduction, [507]

Polypostia, [19];

penes, [27]

Polystomatidae, [53], [55], [73]

Polystomatinae, [73]

Polystomum, [55], [57];

life-history, [58], [59]

Polyzoa, [465] f., [475];

external characters, [465] f., [479] f.;

anatomy, [468] f., [469];

brown bodies, [471] f., [472];

history, [474] f.;

classification, [475] f., [515], [517] f.;

occurrence, [477] f.;

avicularia and vibracula, [482];

enemies, [486];

Entoprocta, [487];

fresh water, [492] f.;

reproduction, [501], [506];

development, [509];

affinities, [461], [509], [510];

metamorphosis, [512];

budding, [514];

distribution, [493], [504], [519];

palaeontology, [520];

terminology, [523];

determination of British genera, [505], [521], [525]

Pomatoceros, habitat, [300], [340]

Pompholyx, [201], [203], [225]

Pontobdella, [393], [401], [404], [406]

Pontodora, [314]

Pontodrilus, [366], [370], [383]

Pontoscolex, [350], [366], [387] f.;

chaeta, [351]

Pore, in Polyzoa, [471], [482], [522], [524];

median, [484], [524];

dorsal, [348]

Porella, [516], [518], [522], [527], [529]

Porina, [518], [527], [529]

Potamilla, [338]

Praeoral lobe (= Prostomium), [245], [439]

Predaceous worms, [304]

Priapuloidea, [412], [446];

anatomy, [430];

classification, [432];

habits, [433]

Priapulus, [430], [431], [432];

anatomy, [430] f.

Pristina, [377]

Proales, [204], [224], [226], [227]

Proboscidae, [49];

occurrence, [44]

Proboscis, of Nemertinea, [100], [101] f., [103] f.;

of Hoplonemertea, [104], [110];

opening by mouth, [117], [119];

severance of, [116];

of Acanthocephala, [174] f.;

of Rotifers, [203];

of Kinorhyncha, [237];

of Echiuroidea, [434]

Proboscis-pore of Nemertinea, [102], [103]

Proboscis-sheath of Nemertinea, [103], [103] f.

Procerodes, [42]

Procerodidae, [42]

Procerus, host of Gordius, [172]

Procotylea, [36], [42]

Proglottis, [5], [74], [75], [79], [85]

Promesostoma, occurrence, [44];

British species, [49]

Proporidae, [49]

Proporus venenosus, [49]

Prorhynchidae, [49]

Prorhynchus sphyrocephalus, terrestrial habit, [44];

P. stagnalis, [49]

Prosorhochmus claparedii, [110], [114], [117]

Prostate-gland, of Leptoplana, [16];

of Polyclads, [30];

of Planaria, [39];

of Rhabdocoela, [47];

of Oligochaeta, [361]

Prostheceraeus, [19], [22];

spermatophores, [27]

Prosthiostomatidae, [19]

Prosthiostomum, [17], [18], [19], [24]

Prostomial tentacles, [248], [262]

Prostomium, [241];

of Dinophilus, [243];

of Polygordius, [244];

of Trochosphere, [245];

of Nereis, [248];

of Polychaeta, [259];

of Glyceridae, [320];

of Terebellidae, [327];

of Oligochaeta, [348]

Protodrilus, [242], [244]

Protonemertini, [112]

Protula, [341];

genital organs, [273], [274];

eggs, [275]

Prouho, on Polyzoa, [489], [507] f.

Provisional chaetae, [274]

Provortex, British species, [50]

Proxenetes, [44];

British species, [49]

Pruvot, on Polychaeta, [261]

Psamathe, [300], [308]

Psammolyce, [313];

elytra, [294], [313]

Pseudalius, [135], [142], [163]

Pseudaxine, [73]

Pseudoceridae, [19], [20]

Pseudoceros, [19], [20]

Pseudocotyle, [73]

Pseudorhynchus bifidus, [49]

Psygmobranchus, [341]

Pterobranchia, [461]

Pterodina, [200], [201], [203], [206], [211], [215], [216], [225], [226], [230]

Pterodinidae, [201], [225]

Pteroessa, [224]

Pteronella, [73]

Pterostichus niger, infested by Gordius, [170], [170], [172]

Pterosyllis, ciliated lappets, [273] n.

Pyriform organ, [509], [511]

Quatrefages, on Gephyrea, [411], [445]

Rabbit, parasites of, [141], [145]

Ragworm, [322]

Railliet, on Cestodes, [91]

Rami, in Rotifers, [210]

Rasping plate, of Eunicidae, [270]

Rattulidae, [210], [225]

Rattulus, [212], [225], [226]

Ratzel, on Earthworms, [350]

Red Cat, [316]

Regeneration of lost parts, in Polyclads, [26];

in Triclads, [40];

in Cestodes, [77];

in Nemertinea, [115];

in Polychaeta, [278], [282];

in Oligochaeta, [348], [379];

in Polyzoa, [471], [488]

Repetition of parts, [249]

Replacement of species, [300]

Reproduction (and Reproductive organs), of Leptoplana, [14] f.;

of Polyclads, [26], [30];

of Triclads, [31], [38], [39];

of Rhabdocoelida, [45], [47] f.;

of Temnocephala, [54];

of Polystomatidae, [57] f.;

of Diplozoon, [60];

of Digenea, [65];

of Calliobothrium, [75];

of Schistocephalus, [86];

of Mesozoa, [93] f.;

of Nemertinea, [102], [103], [104], [109];

of Nematoda, [134];

of Nematomorpha, [166], [169];

of Acanthocephala, [178];

of Chaetognatha, [188];

of Rotifera, etc., [216], [234], [238];

of Archiannelida, [243] f.;

of Polychaeta, [253], [254], [256], [269], [273];

of Myzostoma, [343];

of Oligochaeta, [360];

of Leeches, [401];

of Gephyrea, [418], [431], [437];

of Phoronis, [457];

of Polyzoa, [471], [490], [501], [506]—see also Ovary and Asexual reproduction

Reptiles, parasites of, [163]

Respiration, in Nereis, [252];

in Chaetopoda, [272];

in Gephyrea, [416]

Retepora, [479], [515], [518], [527]

Rhabdites (rods), of Leptoplana, [11], [12];

in Polyclads, [29];

in Triclads, [37];

absent in parasitic Rhabdocoela, [45];

in Temnocephala, [53], [54]

Rhabditiformae, [137]

Rhabditis, [154], [160];

R. nigrovenosa, [140], [155]

Rhabdocoelida, [4], [7], [36], [42] f.;

occurrence and habits, [43];

parasitic forms, [44];

reproduction, [47];

classification, [49];

British species, [43], [44], [49]

Rhabdogaster, [158]

Rhabdonema nigrovenosum, [134], [136], [140], [151], [160], [161]

Rhabdopleura, [461] f.

Rhinodrilus, [348]

Rhinopidae, [220] n., [224]

Rhinops, [224];

male of, [223] n.

Rhizopoda, as food for Polychaeta, [296]

Rhizota, [220] n.

Rhombogen (form of Dicyemid), [93]

Rhopalonaria, [521] n.

Rhopalophorus, [73]

Rhopalura giardii, occurrence and structure, [94], [95];

R. intoshii, [94]

Rhynchelmis, [365], [376]

Rhynchobdellae, [396] f., [405]

Rhynchodemidae, [35], [42]

Rhynchodemus, [34], [35], [42]

Rhynchopora, [531]

Rhynchozoon, [529] n., [531]

Riches, on British Nemertinea, [110];

on Malacobdella, [119]

Rietsch, on Gephyrea, [443]

Rockworm, [319]

Rods—see Rhabdites

Rohde, on muscles of Nematoda, [128] f.

Rootlet, in Polyzoa, [485], [517]

Rosa, on Oligochaeta, [364], [380], [385], [390]

Rosette-plates, [471], [522]

Rotifer, [201], [202], [210], [216], [222], [226], [227]

Rotifera, [197] f.;

distribution, [200];

parasitic, [204];

digestive organs, [209];

renal organs, [213];

nervous system and sense organs, [215];

reproduction and development, [216];

classification, [220];

habits [226];

preservation, [228];

affinities, [229]

Rousselet, on Rotifers, [198], [216], [228]

Sabella, [299], [337]; parapodium, [265];

habitat, [286];

tube, [287];

tube-building, [288];

colour, [293], [294];

S. saxicava, habits of, [287]

Sabellaria, [341];

body, [259];

cirri, [265].;

tube, [287], [290];

S. alveolata, [259], [300];

S. spinulosa, paleae, [267], [300]

Sabellidae, [258], [336];

head, [261];

chaetae, [266], [267];

regeneration, [283];

from fresh water, [284];

colour, [292]

Sabelliformia, [258], [306], [336];

chlorocruorin in, [252]; body, [259];

head, [260], [261];

uncini, [266], [267];

nephridia, [269], [306];

genital organs, [273];

development of gills, [275];

gland shields, [287]

Saccobdella, [226]

Sacconereis, [275], [276], [280]

Saccosoma, [434], [440], [442]

Sagitella, [321]

Sagitta, [186], [186], [191], [534];

anatomy, [186] f., [188];

development, [189];

habits, [190];

species, [191], [193];

American species, [534]

Salensky, on development of Nemertinea, [99];

of Rotifers, [218]

Salinella, [93], [96]

Salivary glands, in Polyclads, [10], [24];

in Leeches, [396]

Salmacina, [273], [341];

brood-pouch, [276];

fission, [281]

Salpina, [200], [225]

Salpinidae, [225]

Sandmason, [328]

Saxicava, Eulalia in borings of, [314]

Scales, of Gastrotricha, [233]

Scalibregma, [334]

Scalibregmidae, [258], [334]

Scapha, [259], [330]

Scaridium, [201], [207], [225]

Schistocephalus, [75], [91];

reproductive organs, [86];

larva, [84];

life-history, [78], [85]

Schizocerca, [225]

Schizogamy, in Syllidae, [278], [279], [281]

Schizonemertea, [109];

characters, [111];

development, [113];

transverse section, [103]

Schizoporella, [518], [527], [528], [529], [530], [531];

zooecium and avicularia, [482];

Leptoplana on, [22]

Schizotheca, [482], [518], [529]

Schmarda, on Oligochaeta, [366], [387]

Schmidt, on Rhabdocoels, [6]

Schneider, on life-history of certain Mesostoma, [48];

on classification of Nematoda, [129];

on oesophageal glands, [131];

on Strongylidae, [142]

Schultze, on Polyclads, [13], [26];

on Nemertinea, [108], [109]

Schultzia, [50]

Schulze, F. E., Stichostemma found by, [118];

Trichoplax found by, [96]

Scirtopoda, [200], [201], [203], [206], [207], [223]

Sclerocheilus, [334]

Sclerostomum, [163]

Scoleciformia, [258], [305], [331] f.;

vascular system, [252];

buccal region, [269];

food of, [296]

Scolecolepis, [299], [322]

Scolex, [5], [74], [75] f., [89];

S. polymorphus, [77];

of Taenia solium, [79]

Scolithus, [302]

Scoloplos, [299], [321];

parapodium, [265];

habitat, [286]

Scruparia, [527]

Scrupocellaria, [517], [518], [519], [526];

vibracula, [477], [485], [517];

phosphorescence, [478];

larva, [511]

Scutum, [525]

Seals, parasites of, [142], [183]

Sea-mat, [466], [477]

Sea-mouse, [312]

Secondary orifice, [522], [524]

Sedentaria, [285]

Segment, [241];

of Nereis, [246], [247]

Seison, [226]

Seisonaceae, [204], [216], [220] n., [225], [227]

Seisonidae, [226]

Selenaria, [518];

vibracula, [487]

Selenka, on Sipunculids, [424] n., [447]

Self-fertilisation, in certain Mesostoma, [48];

in Trematodes, [52], [58];

in Cestodes, [86]

Semper, on excretory system of Nemertinea, [108];

on Geonemertes palaensis, [101] n., [117];

on mimicry in Polychaeta, [294]

Sense-organs, of Leptoplana, [13];

of Polyclads, [26];

of Triclads, [36];

of Trematodes, [56], [86];

of Cestodes, [86];

of Nemertinea, [106];

of Nematoda, [128];

of Gordius, [166];

of Acanthocephala, [178];

of Chaetognatha, [188];

of Rotifera, etc., [215], [233], [234];

of Polychaeta, [255], [272];

of Oligochaeta, [354];

of Leeches, [395];

of Gephyrea, [417];

of Phoronis, [457]

Septum, of Archiannelida, [244];

of Nereis, [249], [251];

of Polychaeta, [269];

of Chlorhaemidae, [334];

of Oligochaeta, [355];

of Gephyrea, [440]

Serpula, [300], [339], [340];

fossil, [301];

tubes, [290], [301];

commensal with Polynoid, [298];

colour, [292]

Serpulidae, [258], [339];

nerve cords, [255];

gills, [261];

operculum, [261];

cirri, [265];

thoracic membrane, [266];

uncinus, [267];

fission, [281];

tube, [290];

colour, [292], [293];

from great depth, [300];

fossil, [301]

Serpulite chalk, [301]

Seta, of vibraculum, [484], [485], [486], [517], [524]

Setosella, [530]

Sharks, Trematodes of, [62], [72];

Cestodes of, [78]

Sheep, parasites of, [67], [81], [82], [83]

Sheldon, Miss, on Nemertinea, [99] f.

Shell-gland, of Leptoplana, [8], [9], [14], [16];

of Polyclads, [28];

of Trematodes, [59];

of Cestodes, [86]

Shield, cuticular, of Polychaeta, [259];

of Sternaspis, [335];

glandular—see Gland shields.

Shipley, on Bipalium, [37];

on Nemathelminthes, [123] f.;

on Chaetognatha, [186] f., [534];

on Gephyrea, [411] f.;

on Phoronis, [450] f.

Sialis lutaria, host of Gordius, [171], [172];

host of Acanthocephala, [185]

Side organs, of Carinellidae, [107]

Siebold, von, on Tape-worms, [76]

Sigalion, [313]

Silliman, on Nemertinea, [101], [109], [118]

Silurian, Polychaeta, [301]

Sinus, in Polyzoa, [482], [484], [525]

Siphon, of Capitelliformia, [272], [305];

of Gephyrea, [436]

Siphonogaster, [353], [368]

Siphonostoma, [334];

commensal, [298]

Sipunculoidea, [412], [420], [446];

species, [426]

Sipunculus, [425];

history, [411];

species, [426];

anatomy, [412] f., [413], [415];

development, [419], [419];

food, [422];

habits, [426]

Size, of Cestodes, [5];

of Polyclads, [20];

of Land Planarians, [33];

of Cestodes, [75];

of Nemertinea, [100]

Slavina, [377]

Sluiter, on Gephyrea, [429], [447]

Smitt, on Polyzoa, [516]

Smittia, [518], [527], [529];

zooecium and avicularium, [482]

Snakes, parasites of, [142]

Solenopharyngidae, [50]

Solenopharynx, [50]

Solenophorinae, [91]

Solenophorus, [91]

Sorocelis, [42]

Spadella, [186], [189], [192];

anatomy, [186] f.;

eggs, [189];

habits, [190];

species, [192], [194];

American species, [534]

Spallanzani, on Oligochaeta, [348]

Sparganophilus, [366], [386];

anatomy, [355].

Spatangus, as host, [298]

Spencer, on Land-Planarians, [34];

on earthworms, [349], [380]

Spengel, on Gephyrea, [440]

Spermatheca, of Dinophilus, [243];

of Oligochaeta, [362], [363], [364]

Spermatophores, [27], [402]

Spermiducal gland, [361]

Sphaerodoridae, [320]

Sphaerodorum, [321]

Sphaerosyllis, [308]

Sphaerularia, [150], [153], [160], [161]

Sphyranura, [73];

setae in, [56]

Spine, of Polyzoa, [481], [523] f., [524]

Spinther, [318]

Spio, [322]

Spionidae, [258], [321];

larva, [274], [275]

Spioniformia, [258], [304], [321];

peristomial cirri, [263];

gill, [265];

chaetae, [266], [267];

eyes, [272];

food, [296]

Spirographin, [290]

Spirographis, [338];

substance of tube, [290]

Spiroptera, [147], [163];

S. reticulata, [149];

S. obtusa, [161];

S. alata, [163]

Spirorbis, [340], [341];

operculum, [261], [341];

genital organs, [273], [274];

brood-pouch, [261], [276];

fossil, [301]; shell, [341]

Spirosperma, [378];

chaeta, [350]

Spirulaea, [301]

Sporocysts, [92];

of Distomum macrostomum, [64], [65];

of D. hepaticum, [67];

hosts of, [71]

Staggers, induced by Coenurus, [82]

Statoblast, [493], [499], [501] f., [506];

sessile, [502];

germination, [501], [503], [514];

resemblance to ephippian ova, [493]

Steenstrup, on Tape-worms, [76]

Steganoporella, [530]

Stelechopoda, [344]

Stelechopus, [342]

Stenostoma, [44], [49];

asexual reproduction, [44]

Stephanoceros, [202], [205], [210], [213], [220], [221]

Stephanops, [225]

Stercutus, [376]

Sternaspidae, [258], [335];

nephridia of, [305]

Sternaspis, [335], [411], [445];

anatomy, [335], [336];

shape, [259];

shield, [259];

head, [264];

chaetae, [265];

gills, [268];

intestine, [271];

compared with Gephyrea, [336], [447], [449]

Sthenelais, [299], [300], [309], [313]

Stichostemma eilhardii, [118]

Stilesia, [91];

generic characters, [90];

S. centripunctata, [91];

S. globipunctata, [91]

Stock, asexual, of Autolytus, [279];

of Myrianida, [281]

Stolc, on Oligochaeta, [360]

Stolon, [480], [488], [518], [525]

Stolonata, [518] n.

Stomatopora, [518], [532]

Stork, parasites of, [63], [163]

Strobila, [75], [76]

Strobilation, [76]

Strodtmann, on Chaetognatha, [191]

Stromatoporoids, [520]

Strongylidae, [131], [142]

Strongylus, [129], [142], [143], [160], [163];

S. filaria, [132];

S. tetracanthus, [163]

Stuhlmann, on Polyzoa, [493]

Stuhlmannia, [359], [386]

Stylaria, [348], [377]

Stylets of Nemertine proboscis, [104], [110]

Stylochoplana, [18], [19], [20]

Stylochus, [19];

development, [28]

Stylostomum, [19], [22]

Sub-cuticle, [125], [175]

Submalleate, [210], [211]

Succinea putris, infested by larvae of Distomum macrostomum, [64], [66]

Sucker, of Leptoplana, [8], [16] n.;

of Triclads, [35], [36];

of Temnocephala, [53], [54];

of Monogenea, [53], [56], [57], [60];

of Digenea, [62], [64], [65], [69];

of Cestodes, [75], [79];

of Dinophilus, [243];

of Chaetopterus, [324];

of Myzostoma, [342];

of larva of Polyzoa, [509], [511]

Summer-eggs, of Mesostoma, [48];

of Rotifera, [216]

Sutroa, [376], [380]

Swim-bladder, of Syllidae, [272]

Swimming, of Leptoplana, [9], [10];

of Polyclads, [23];

of Rotifers, etc., [206], [235]

Syllidae, [258], [306];

palps, [260];

tentacles, [262];

head, [262];

parapodium, [264];

jaw, [270], [271];

alimentary tract, [271];

swim-bladder, [272];

asexual reproduction, [278] f., [279];

regeneration, [278], [283];

colours, [293];

phosphorescence, [296];

ancestral, [303]

Syllis, [274], [307];

development, [278];

S. armillaris, [307];

S. ramosa, [282];

S. vivipara, [276]

Synapta, bearing Rotifers, [222], [227]

Synchaeta, [200], [204] f., [224], [226]

Synchaetidae, [223], [224]

Syncoelidium, [33], [42]

Syncytium, [125]

Syngamus trachealis, [130], [142], [144], [161], [163], [164]

Syrinx, [411]

Taenia, [74], [78], [79], [91];

life-histories of species of, [83];

table of species, [89];

T. (Cysticercus) acanthotrias, [80];

T. coenurus, [81], [82];

life-history, [83];

specific characters, [90];

T. crassicollis, life-history, [78], [83];

specific characters, [89];

T. echinococcus, [80];

life-history, [83];

specific characters, [90];

T. krabbei, [81];

T. marginata, [81];

life-history, [83];

specific characters, [90];

T. (Hymenolepis) murina, [70], [80] n., [89];

life-history, [80], [83];

specific characters, [91];

T. perfoliata, [163];

T. saginata (= T. mediocanellata), [78], [79];

life-history, [83];

specific characters, [89];

T. serialis, [82];

life-history, [83];

specific characters, [90];

T. serrata, [81];

life-history, [83], [87], [89];

specific characters, [90];

T. solium, [79];

life-history, [79], [83];

specific characters, [89]

Taeniasis, [82]

Taeniidae, [91]

Tail, of Arenicola, [333];

of Nereis, [246], [248];

regeneration of, [283]

Tanypus, host of Gordius, [172]

Tape-worms, [5], [74]

Taphrocampa, [200], [204], [224]

Tardigrada, affinities, [344]

Telmatodrilus, [378]

Temnocephala, [4], [53], [54], [73]

Temnocephalidae, [53], [73];

habits and structure, [53] f.;

affinities, [54]

Tennent, on land-leeches, [408]

Tentacles, in Polyclads, [15], [26];

in Triclads, [30], [36];

in Vorticeros, [45], [46];

in Trematodes, [53];

(peristomial), of Spionidae, [322];

(prostomial), [255], [260], [262] f.;

of Nereis, [248];

of Polycirrus, [294], [295];

of Polygordius, [244];

of Terebellids, use of, [289];

nerves to, [254]

Tentacle-sheath, in Polyzoa, [470]

Tentacular cirri = Peristomial cirri, q.v.

Tentacular filaments, [304];

of Cirratulids, [326], [327]

Terebella, [328];

otocyst, [273];

fossil, [301];

T. conchilega, tube, [286], [287], [288];

building of tube, [289], [290];

gill, [329];

T. nebulosa, colour, [292];

as host, [311];

gill, [329]

Terebellidae, [258], [327];

shape, [259];

tentacles, [263];

gill, [265];

chaetae, [266], [267];

gizzard, [271];

tube, [286];

use of tentacles, [289];

colour, [293];

phosphorescence, [296];

food of, [296];

tube containing Polynoid, [298]

Terebellides, [299], [330];

gill, [329]

Terebelliformia, [258], [325];

definition, [304];

genital organs, [273];

gland shields, [287];

nephridia, [269];

nuchal organs, [273];

uncini, [266], [267];

vascular system, [252]

Terebripora, [478]

Terricola, [30], [42]

Tertiary, Polyzoa, [521]

Tessin, on Rotifers, [198], [218]

Testes, of Leptoplana, [14], [15];

of Planaria lactea, [38], [39];

of Acoela and Alloeocoela, [47];

of Temnocephala, [54];

of Polystomum, [57];

of Cestodes, [75], [76], [86]—see also Reproductive organs

Tetragonurus, [389]

Tetraonchus, [73]

Tetraphyllidae, [91]

Tetrarhynchidae, [91]

Tetrarhynchus, [75], [76] n., [85], [91]

Tetrastemma, British species, [110];

land forms, [101], [115], [118];

fresh-water forms, [101], [118];

excretory system, [108], [109];

habits, [114];

hermaphrodite species, [109];

viviparous species, [117]

Thalamoporella, [530]

Thalassema, [411], [435] f., [441], [443];

development, [439];

habits, [443]

Thelepus, [299], [329]

Theodisca, [321]

Thompson, J. V., on term Polyzoa, [475]

Thoracic membrane, [266], [305]

Thorax, of Polychaeta, [259], [306], [337]

Thysanosoma, [91];

generic characters, [90];

T. fimbriata, life-history, [83];

specific characters, [90];

T. giardii, specific characters, [90]

Thysanozoon, [13], [18], [19], [20]

Tomopteridae, [258], [291], [315]

Tomopteris, [315];

colour, [294];

light-producing organ, [296];

prostomium, [259];

T. rolasi, [315]

Tooth, in Polyzoa, [482], [522]

Tortoise, Temnocephala associated with, [53]

Torus uncinigerus, [268]

Tracks, fossil, [302]

Travisia, [332]

Travisiopsis, [321]

Trematoda, [4], [51] f.;

life-histories, [71];

classification, [73]

Trembley, on Turbellaria, [6];

on Polyzoa, [496], [497]

Trepostomata, [520]

Triaenophorus (= Tricuspidaria), [91];

excretory system, [84]

Triarthra, [201], [203], [206], [211], [224], [225], [226]

Triarthridae, [200], [201], [202], [206], [207], [224], [226]

Trias, Serpulid in, [301]

Trichina, [131], [135], [144], [161];

T. spiralis, [146], [163]

Trichinosis, [82], [146], [147]

Trichocephalus, [131], [135], [136], [144], [160], [163];

species of, [145];

T. dispar, [145]

Trichochaeta, chaeta, [351]

Trichoderma, [159]

Trichoplax, [93], [95]

Trichosoma, [144], [163];

species of, [145]

Trichotrachelidae, [144]

Tricladida, [7], [30] f.;

habits, [35] f.;

sexual reproduction, [38];

asexual reproduction, [40];

classification, [42];

British species, [31], [32], [34], [42]

Tricoma cincta, [157]

Tricuspidaria, [91]

Trigaster, [359], [384]

Trigonoporus, [19], [27]

Trinephrus, [357], [382] f.

Triophthalmus, [224]

Triphylus, [224]

Tristicochaeta, [158]

Tristomatidae, [53], [55], [73]

Tristomatinae, [73]

Tristomum, [73]

Triticella, [478], [518], [533]

Trocheta, [393], [407]

Trochophore, [229]

Trochopus, [73]

Trochosphaera, [200], [201], [221], [229], [230]

Trochosphaeridae, [221]

Trochosphere, of Archiannelida, [243], [245];

of Polychaeta, [274], [275], [510], [512];

of Echiuroidea, [439], [510];

of Polyzoa, [510]

Trochus, in Rotifers, [202], [204]

Trophi, of Rotifers, [209], [210]

Trophonia, [299], [334];

genital organs, [273];

head, [262];

intestine, [271]

Trunk, of Nereis, [246];

of Polychaeta, [259];

of Gephyrea, [412] f.

Tube, of Rotifers, [205];

of Polychaeta, [287] f.; composition of, [290];

fossil, [301], [302];

of Chaetopterus, [323];

of Clymene, [287];

of Dodecaceria, [326];

of Eunice tibiana, [290];

of Eunicidae, [285], [290], [318];

of Haplobranchus, [339];

of Hekaterobranchus, [326];

of Hyalinoecia, [290], [319];

of Maldanidae, [332];

of Myxicola, [285], [338];

of Nereis, [316];

of Nicomache, [287];

of Onuphis, [287], [319];

of Owenia, [325];

of Pectinaria, [285], [288], [330];

of Polydora, [323];

of Polynoids, [285];

of Panthalis, [313];

of Sabella, [287] f.;

of Sabellaria, [287];

of Sabellidae, [337];

of Serpulidae, [290], [339] f., [340];

of Terebellidae, [286], [287], [288], [289], [327] f.;

of Priapuloidea, [433];

of Echiurus, [444]

Tube-forming glands, [304]

Tube-making, of Polychaeta, [287] f.

Tubicolous Polychaeta, [285], [300], [304], [306]

Tubifex, [351], [367], [369], [378];

chaetae, [350]

Tubificidae, [350], [361], [366], [378]

Tubulipora, [518], [531], [532]

Turbellaria, [3] f.

Turtles, parasites of, [142]

Tylenchus, [131], [154], [155], [157], [160], [163]

Tylosoma, [422], [423], [426], [430], [447]

Typhloscolecidae, [258], [291], [321];

nuchal organ, [273] n.

Typhloscolex, [321]

Typosyllis, regeneration of head, [283] n.

Udekem, D', on Oligochaeta, [365]

Udonella, [73];

U. caligorum, [55];

U. pollachii, eggs of, [58]

Udonellinae, [73]

Umbonula, [531]

Uncinaria, [143]

Uncinate, [210], [211]

Uncini, of Polychaeta, [266], [267], [304], [305]

Uncus, [210]

Urnatella, [490], [493], [518]

Urobenus, [388]

Uteriporus, [42]

Uterus, of Leptoplana, [8], [14];

of Planaria, [38], [39];

of Triclads, [40];

of Rhabdocoela, [48];

of Temnocephala, [54];

of Polystomum, [57], [59];

of Diplozoon, [60];

of Didymozoon, [71];

of Calliobothrium, [75];

of Taenia, [79];

of Schistocephalus, [86];

in Bothriidae, [87];

of Rotifers, [216]

Vagina, of Leptoplana, [16];

in ectoparasitic Trematodes, [57] f.;

in Cestodes, [86], [87]

Vaillant, on Hirudinea, [392], [405]

Valencinia, [113];

V. lineformis, [112]

Valkeria, [533]

Vallentin, on Rotifers, [198]

Vallisnia, [73]

Vanadis, [315]

Varme, [297]

Vasa deferentia, of Leptoplana, [14], [15];

of Planaria, [38], [39];

of Acoela and Alloeocoela, [47];

of Diplozoon, [60];

of Schistocephalus, [86]

Vasa efferentia, of Leptoplana, [14], [15];

of Triclads, [38]

Vascular System, of Nemertinea, [106], [107];

of Archiannelida, [244];

of Nereis, [251] f.;

of Polychaeta, [251] f.;

of Cryptocephala, [252];

of Scoleciformia, [252];

of Terebelliformia, [252];

absence of, in certain Polychaeta, [253];

of Oligochaeta, [355];

of Leeches, [396];

of Gephyrea, [415], [436], [447];

of Phoronis, [455]

Vaucheria, Rotifers in, [227]

Vejdovsky, on Rhabdocoels, [46];

on Gordius, [164], [166];

on Oligochaeta, [365], [369], [374], [400]

Vermes, [347]

Vermiculus, [378]

Vermiformia, [461]

Verrill, on Chaetognatha, [534]

Vertebrates, parasites of, [163], [174], [179], [183]

Verworn, on statoblasts, [501]

Vesicula seminalis, of Planaria, [39]

Vesicularia, [481], [518], [533]

Vesicularina, [518], [523]

Vestibule, [488], [490];

of larva, [509]

Vibracular zooecium, [485], [486], [517], [524]

Vibraculum, [477], [484], [485], [517], [524];

movements, [487];

function, [486]

Vicarious avicularia, [482]

Victorella, [492], [501], [505], [518], [533]

Villot, on life-history of Gordius, [172]

Vinella, [521] n.

Virgate, [210]

Visceral nervous system, of Nereis, [255]

Vitellarium = Yolk-gland, q.v.

Vitello-intestinal canal, in Polystomatidae, [57]

Viviparous, Nemertinea, [109], [117];

Rotifers, [200], [216] f.;

Polychaeta, [256], [276]

Volvox, Rotifers in, [227]

Vortex, [44];

British species, [50];

body-cavity, [43]

Vorticellids, on Polychaeta, [299]

Vorticeros, British species, [45], [46], [50]

Vorticidae, [50]

Vuillemin (misprinted in text), on Nematodes in deserts, [156]

Walford, on Polyzoa, [521]

Ward, on Nectonema, [168];

on Sipunculus, [417]

Warning colours, in Polychaeta, [294], [314]

Waters, on Polyzoa, [517]

Wheeler, on Myzostomaria, [344]

Whelk, shell occupied by Nereis, [298]

White Cat, [317]

Whitman, on Dicyemidae, [94];

on Hirudinea, [395] f., [402], [405] f.

Willemoes-Suhm, von, on Tetrastemma agricola, [101], [115], [117], [118]

Willey, on affinities of Nemertinea, [120] n.;

on Oligochaeta, [382]

Wings, of Chaetopterus, [295], [324]

Winter-eggs, of Mesostoma, [48];

of Rotifers, [217];

compared with statoblasts, [493]

Woodworth, on yolk-glands, [38] n.

Wreath, in Rotifers, [200]

Wright, on Phoronis, [450], [456]

Yellow-cells, in Leptoplana, [13]

Yolk-gland, in Planaria, [38], [39];

in Rhabdocoelida, [47];

in Temnocephala, [54];

in Polystomatidae, [57];

in Calliobothrium, [75];

in Schistocephalus, [86];

in Rotifers, [199], [216]

Yoruba Worm, [368], [387]

Youatt, on Coenurus, [82]

Yungia, [19], [25]

Zebra, parasites of, [140]

Zelinka, on Rotifers, [198], [215] n., [218], [219], [227], [229];

on Gastrotricha, [232]

Zooecium, [466], [469], [474], [488], [523];

of Phylactolaemata, [495];

loss of zooecia, [481], (= calyces), [488];

primary, [506];

alterations with age, [522]

Zone of budding, [279], [283]

Zooid, sexual and asexual, [278] f.

Zoophytes, [465], [474]

END OF VOL. II

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NOTES

[1]

Hemprich and Ehrenberg, Symbolae physicae, Berlin, fol. 1831.

[2]

Τρῆμα, a hole; referring to the orifices of the suckers.

[3]

Mémoires pour servir à l'histoire d. Polypes d'eau douce, Leyden, 1744.

[4]

Die Parasiten des Menschen, 1879——. Engl. Transl. by W. E. Hoyle, i. 1886.

[5]

Band 4, by M. Braun. (Mesozoa and Trematoda completed; Cestoda in progress.)

[6]

Verm. terr. et fluv. ... succincta historia, 1773; Zool. Danica, 1777.

[7]

Observations on Planariae, Edinburgh, 1813.

[8]

M. Faraday, "On the Planariae," Medical Gazette, Feb. 1832; and in Edinburgh New Philosoph. Journal, vol. xiv. 1833, pp. 183-189.

[9]

Nov. Act. Acad. Caes. Leop.-Carol. tom. xiii. 1827.

[10]

Ann. Sci. Nat. (Zool.) I. tom. xv. 1828.; ibid. tom. xxi. 1830.

[11]

Mém. Acad. St. Pétersbourg, 5th ser. tom. ii. 1832.

[12]

Die rhabdocoelen Turbellarien des Süsswassers. Jena 1848.

[13]

Monographie d. Turbellarien. I. Rhabdocoelida, 1882. Die Acoela, Leipzig, 1892.

[14]

"Die Polycladen," Fauna u. Flora d. Golfes v. Neapel, Monogr. XI. 1884.

[15]

Phil. Trans. 1874, p. 105.

[16]

Since no food, but only the pharynx, passes through this "mouth," the term is unfortunate. Moreover the true mouth is the aperture placing the stomach in communication with the pharynx (Fig. 5, gm).

[17]

Ann. Sci. Nat. 1 sér. tom. xv. 1828, p. 146. "La Planaire trémellaire ... peut parcourir ... en faisant battre rapidement ses parties latérales à la manière des larges nageoires des Raies."

[18]

Observations on Planariae. Edinburgh, 1813, p. 12.

[19]

"Zur Anat. u. Entwickl. einiger Seeplanarien v. St. Malo," Abh. K. Gesellschaft d. Wiss. Göttingen, 1868.

[20]

The roof of the peripharyngeal chamber is hence known as the "diaphragm."

[21]

See Brandt, Fauna u. Flora d. Golfes v. Neapel, Monogr. XIII. 1885, p. 65.

[22]

See p. [94].

[23]

Verhandlungen d. med. Gesellschaft zu Würzburg, iv. 1854, p. 223.

[24]

Enantia spinifera Grff. Mittheil. d. Naturwiss. Verein. f. Steiermark, 1889.

[25]

The sucker of Leptoplana tremellaris probably does not correspond with that of the Cotylea.

[26]

Collingwood, Trans. Linn. Soc. 2 ser. vol. i. pt. 3, 1876, p. 83.

[27]

Von Stummer-Traunfels, Zeitschr. f. wiss. Zool. Bd. lx. 1895, p. 689.

[28]

Planocera pellucida Mertens, P. simrothi v. Grff., P. grubei Grff., Stylochoplana sargassicola Mertens, S. californica Woodworth, Planctoplana challengeri Grff., all belonging to the Planoceridae. See v. Graff, "Pelagische Polycladen," Zeitschrift f. wiss. Zoologie, Bd. lv. 1892, p. 190.

[29]

Cambridge Natural History, vol. iii. p. 74.

[30]

Lang, "Polycladen," p. 629.

[31]

Wheeler, Journal of Morphology, vol. ix. part 2, 1894, p. 195.

[32]

Many Nudibranchiate Mollusca undergo this change of habitat. See Garstang, Journal of the Marine Biological Assoc. n.s. i. No. 4, 1890, p. 447.

[33]

Chun, "Ctenophoren," Fauna u. Flora G. v. Neapel, Monogr. I. 1880, p. 180.

[34]

See Lang, "Polycladen," p. 607.

[35]

Lang, "Polycladen," Pl. 30, Fig. 8.

[36]

Kongl. Fysiograf. Sällskapets Handlingar, Bd. iv. Lund, 1892-93.

[37]

Whitman, Journal of Morphology, vol. iv. 1890, p. 361.

[38]

A full account of Polyclad development is contained in Lang's "Polycladen," with references to the literature of the subject. Since the date of that work (1884) the embryology of Ctenophora has become better known, but, though the segmentation of the egg and early stages of development are very similar in both cases, the elaborate investigations of E. B. Wilson (Journ. Morphology, vol. vi. p. 361) show that the segmentation of Polychaet worms is again similar. The question of the affinities of the Polycladida is also discussed by Lang ("Polycladen" p. 642 et seq.). The work of the last decade has neither proved nor disproved his suggestion that the Ctenophores and Polyclads have been derived from common ancestors. On this subject the remarks made by Hatschek (Lehrbuch d. Zoologie, p. 319) are some of the weightiest that have appeared.

[39]

Hallez, Revue Biologique du Nord de la France, tom. ii. 1889-90.

[40]

Voigt, Zool. Anz. xv. p. 238.

[41]

Grube, Archiv f. Naturgeschichte, 38 Jahrg. Bd. i. 1872, p. 273.

[42]

Vejdovsky, Zeitschr. f. wiss. Zoologie, Bd. lx. 1895, p. 200.

[43]

Woodworth, Bulletin Mus. Comp. Zoology, Harvard, vol. xxi. No. 1, 1891.

[44]

Mitth. Zool. Stat. Neapel, 1882, p. 187.

[45]

Wheeler, Journal of Morphology, vol. ix. 1894, p. 167.

[46]

Dendy, Trans. Roy. Soc. Victoria 1890, p. 65; Id. Austral. Assoc. Brisbane, 1895, "Presid. Add. to Sect. D," p. 15.

[47]

Darwin, Ann. and Mag. Nat. Hist. vol. xiv. 1844, p. 241.

[48]

Shipley, Proc. Camb. Phil. Soc. vol. vii. pt. 4, 1891 (with literature).

[49]

Trans. Roy. Soc. Victoria from 1889 onwards. Trans. New Zealand Institute, 1894-95.

[50]

Moseley, Phil. Trans. 1874, p. 105; Id. Quart. Journ. Micr. Sci. vol. xlvii. 1877, p. 273; Loman, Bijdrag tot d. Dierkunde, Aflev. 14, 1887, p. 71; Id. Zool. Ergeb. ein. Reise in Nieder-Ost-Indien, Hft. 1, p. 131; Beddard, Zoogeography, 1895, p. 53.

[51]

Beobachtungen ü. Anat. u. Entwickel. an der Küste von Normandie, 1863, p. 18.

[52]

Archiv f. Naturgeschichte, 57 Jahrg. Bd. i. Hft. 3, 1891, p. 308.

[53]

Dendy, Proc. Roy. Soc. Victoria, vol. iv. n.s. i. 1892.

[54]

Schmarda, Neue wirbellose Thiere, Leipzig, 1859, I. i. p. 30.

[55]

Abhandl. d. Naturf. Gesell. zu Halle, Bd. iv. 1857, p. 33.

[56]

Arb. Zool.-Zoot. Instit. Würzburg, Bd. v. 1882, p. 120.

[57]

Woodworth (loc. cit. p. 38) states that in Phagocata the yolk-glands arise by proliferation from two parovaria, placed just in front of the ordinary ovaries. Iijima, however (Zeitschr. f. wiss. Zool. Bd. xl. 1883, p. 454), regarded them as derivatives of the parenchyma.

[58]

The extensive literature on this subject is fairly completely summarised by Voigt in Biol. Centralblatt, vol. xiv. Nos. 20, 21, 1894. Faraday's observations (cf. p. [6], note 8) have been generally overlooked.

[59]

Archives d. Biologie, tom. xii. 1892, p. 437.

[60]

Mitth. Zool. Stat. Neapel, Bd. iii. 1882, p. 187.

[61]

Böhmig, Ergebnisse d. Plankton Expedition, Bd. ii. H. g. 1895.

[62]

von Graff, Die Acoela, Leipzig, 1892. Appendix.

[63]

The development of the Acoela has been worked out recently by Mdlle. Pereyaslawzewa (Zapiski Novoross. Obshch. Odessa, 17 Bd. 1892) and Gardiner (Journal of Morphology, xi. No. 1, 1895, p. 155) with conflicting results. The former finds four endoderm cells, which give rise to a larval intestine. The Acoela are for her, Pseudacoela. Gardiner, on the other hand, finds no trace of an endoderm at any stage of the development of Polychoerus caudatus.

[64]

Tijdschr. Nederland. Dierk. Ver. Deel ii. 1875.

[65]

Von Graff, Monographie d. Turbellarien: I. Rhabdocoeliden, 1882. Gamble, Quart. Journ. Microscop. Science, vol. xxxiv. 1893, p. 433.

[66]

Zeitschr. f. wiss. Zoologie, Bd. lx. 1895, p. 163.

[67]

See von Graffs Monographie, pl. ix.; and Jensen, Turbellaria ad Litora Norvegiae, Bergen, 1878, pl. iv.

[68]

For the reproductive organs of Rhabdocoelida, consult von Graff, Monographie, "Die Acoela"; and Böhmig, Zeitschr. f. wiss. Zool. Bd. li. 1891, p. 167.

[69]

Untersuchungen ü. Platyhelminthen, Giessen, 1873, p. 101.

[70]

Compare the remarks on Trematodes, pp. [4-5].

[71]

Haswell, Monograph of the Temnocephaleae. Macleay Memorial Volume. Mem. iii. 1893.

[72]

Braun, in Bronn's Klassen u. Ordn. d. Thierreichs, vol. iv. p. 407, gives a valuable summary of our knowledge of this group. For figures, see van Beneden and Hesse, Mémoires de l'Acad. roy. de Belgique, tom. xxxiv. 1864, pp. 1-169. A valuable paper (with synoptic tables) on Japanese Monogenea, by Goto, Journ. Coll. Sci. Japan, vol. viii. pt. 1, 1894, has recently appeared.

[73]

See Leuckart, "Parasiten" Bd. ii. p. 238.

[74]

Zeller, Zeitschr. f. wiss. Zool. xxii. 1872, pp. 1, 168; also Bd. xxvii. 1876, p. 238; xlvi. 1888, p. 233.

[75]

An excellent and beautifully illustrated account, by Looss, of the Distomatidae of Frogs and Fishes may be found in Leuckart and Chun's Bibliotheca Zoologica, Heft 16, 1894.

[76]

Leuckart, Parasiten d. Menschen, "Trematoden," 1892-94; R. Blanchard, Traité d. Zool. médicale, i. 1889; H. B. Ward, Report for 1894 of Nebraska State Board of Agric. Lincoln, U.S.A. 1895, p. 225.

[77]

Huxley, Anat. of Invert. Animals, 1877, p. 194.

[78]

Braun, Bronn's Thierreichs, Bd. iv. p. 792; Leuckart, Parasiten d. Menschen, 11 Abth. p. 158; Brandes, in Spengels Zool. Jahrb. Syst. Abtheil. Bd. v. 1890, p. 849; v. Nordmann, Mikr. Beitr. i. Berlin, 1832.

[79]

Heckert, Bibliotheca Zoologica (Leuckart and Chun), Heft 4, 1889. I am not aware that Leucochloridium has been noticed in England.

[80]

"Heterogamy" usually means the alternation of bisexual and unisexual generations (e.g. Rhabdonema nigrovenosum), but is, unfortunately, also used in the sense of Alloiogenesis, as defined above. See Grobben, Arbeit. Zool. zoot. Ints. Wien, Bd. iv. 1881, p. 201.

[81]

Parasiten, Bd. i. Abth. II. p. 152.

[82]

Festschrift f. Leuckart, Leipzig, 1892, p. 167.

[83]

Quart. Journ. Micros. Sci. vol. xxiii. 1883, p. 90.

[84]

The intermediate host in the Sandwich Islands is said to be Limnaea peregra. See Lutz, Centralbl. f. Bakter. xi. 1892, p. 783.

[85]

The mortality in wet years, however, is said to be largely due to pulmonary inflammation. This and other causes of death are not always discriminated in the returns.

[86]

See Thomas, Quart. Journ. Micros. Science, xxiii. 1883. Neumann, Parasites of Domesticated Animals, translated by Fleming, 1892.

[87]

Leuckart, loc. cit.; Looss, Archiv f. mikroskop. Anatomie, Bd. xlvi. 1895, p. 1.

[88]

In Leuckart, Die Parasiten d. Menschen, pp. 521-528, 1894.

[89]

Cf. p. [89].

[90]

See Braun. Bronn's Klassen u. Ordnungen d. Thierreichs, vol. iv. p. 572.

[91]

Braun, loc. cit. p. 573.

[92]

Taken largely from Braun, Ibid. pp. 864-866, where the literature of the subject is referred to fully.

[93]

Festschr. f. Leuckart, 1892, p. 134.

[94]

Cf. p. [5].

[95]

Arbeit. Inst. Wien, iii. 1881, p. 163; see also ibid. ix. 1890, p. 57.

[96]

For figures of various scolices see van Beneden, Mémoire sur les vers Intestinaux, 1861; Braun in Bronn's Thierreich, Cestoda (in progress), Bd. iv. Pl. xxxviii.-xlv.

[97]

The mature proglottis of Calliobothrium eschrichti is 8-9 mm. long, whereas the strobila only measures 4-5 mm. in length. Species of Phylliobothrium, Anthobothrium, and Tetrarhynchus show a similar but not an equal contrast between the size of the parent and proglottis (P. J. van Beneden, "Les Vers Cestoides," Nouv. Mém. de l'Acad. Roy. d. Belgique, tom. xxv. 1850).

[98]

The difficult question of the nature of the Cestode body and Cestode larvae is adequately discussed by Braun, loc. cit. p. 1167.

[99]

Leuckart, Die Parasiten d. Menschen [English trans. by W. E. Hoyle]; Blanchard, Traité de Zoologie médicale, 1893.

[100]

For a full account of the history of this subject see Leuckart, Parasiten d. Menschen, p. 28; Braun, loc. cit. Bd. iv. p. 929 et seq.; Huxley, Collected Essays, vol. viii. p. 229.

[101]

By Grassi this form is considered identical with T. murina. The latter species is known, from this author's researches, to develop in rats without migration into an intermediate host. Should Grassi's synonymy prove correct, the presence of large numbers of this tape-worm in man would readily receive its explanation.

[102]

Leuckart, loc. cit. p. 752 et seq.

[103]

The distinctive features of these and the foregoing tape-worms are given on pp. [89-90]

[104]

For description of the Cercocystis-larva see Villot, Ann. Sci. Nat. (Zool.) (6), xv. 1883, Art 4; and compare Leuckart's criticism of this paper, "Parasiten," p. 979.

[105]

Moniez, "Sur les Cysticerques," Paris, 1880; Id. "Sur les Cestodes," 1881; Zschokke, "Recherches sur la structure anatomique et histologique d. Cestodes," Genève, 1888.

[106]

Schmidt, Archiv f. Naturgeschichte, Jahrg. lx. Bd. 1, 1894, p. 65.

[107]

For example, the genitalia in Dipylidium caninum are duplicated in each proglottis. Other differences are noted in the following table (pp. [89-90]).

[108]

See Stiles, Centralbl. f. Bakt. u. Parasitenkunde, 1893, xiii. p. 457 (conf. note, p. [90]).

[109]

Taken from Neumann, Parasites of Domesticated Animals, 1892, p. 448.

[110]

µ = 1⁄1000 millimetre.

[111]

For a description of these glands, and for further diagnostic details and literature, see Stiles and Hassall, U. S. Department of Agriculture, Bureau of Animal Industry, Bulletin 4, 1893.

[112]

Ed. van Beneden, Bull. Acad. Roy. Belgique, 1876, p. 35.

[113]

Whitman, Mittheil. Zool. Stat. Neapel, Bd. iv.; see also Braun, in Bronn's Thierreich, Bd. iv. p. 253.

[114]

Braun, loc. cit. p. 281 (with literature).

[115]

Giard, "La Castration parasitaire," Bull. Sci. d. France et de Belgique, 3 sér. i. 1888, p. 12.

[116]

Schulze, Abh. Akad. Berlin, 1891, p. 1.

[117]

Arch. Naturg. lviii. 1891, p. 66.

[118]

P. Boston Soc. vol. vi. 1848.

[119]

Zeitschr. wiss. Zool. Bd. v. 1854, p. 344.

[120]

Arch. Anat. 1858, p. 289.

[121]

Ibid. 1858, p. 558.

[122]

Mem. Ac. St. Petersb. ser. vii. tom. xiv. 1869.

[123]

Zeitschr. wiss. Zool. Bd. xliii. 1886, p. 481.

[124]

R. von Willemoes-Suhm, Ann. Nat. Hist. ser. iv. xiii. 1874, p. 409.

[125]

Semper, Zeitschr. wiss. Zool. Bd. xiii. 1863, p. 558.

[126]

L. von Graff, Morphol. Jahrb. Bd. v. 1879, p. 430.

[127]

W. A. Silliman, Zeitschr. wiss. Zool. Bd. xli. 1885, p. 48.

[128]

du Plessis, Zool. Anz. vol. xv. 1892, p. 64.

[129]

J. von Kennel, Arb. Inst. Würzburg, Bd. iv. 1877-78, p. 305.

[130]

H. N. Moseley, Ann. Nat. Hist. ser. iv. vol. xv. 1875, p. 165.

[131]

See Hubrecht, in Verh. Ak. Amsterdam, vol. xx. 1880; and in Quart. J. Micr. Sci. vol. xx. 1880, p. 431.

[132]

"Nemertinen," Fauna und Flora G. von Neapel, 22 Monogr. 1895.

[133]

Beiträge zur Naturgeschichte der Turbellarien, Griefswald, 1851.

[134]

Arb. Inst. Würzburg, Bd. iii. 1876, p. 115.

[135]

Ibid. Bd. iv. 1877, p. 305.

[136]

Zool. Anz. vol. viii. 1885, p. 51.

[137]

Quart. J. Micr. Sci. vol. xxv. 1885, suppl. p. 1.

[138]

Zeitschr. wiss. Zool. Bd. xli. 1885, p. 48.

[139]

Ibid. Bd. liii. 1892, p. 322, and Fauna und Flora G. von Neapel, 22 Monogr. 1895.

[140]

Ann. Sci. Nat. (5) vol. xvii. 1873.

[141]

Zeitschr. wiss. Zool. Bd. iv. 1853, p. 178.

[142]

Our knowledge of British species is mainly due to M‘Intosh (British Annelids, Ray Society, 4to, 1873) and Riches (Journ. Mar. Biol. Ass. vol. iii. 1893-1895, p. 1).

[143]

Fauna und Flora G. von Neapel, 22 Monogr. 1895.

[144]

See M‘Intosh, British Annelids, Ray Society, 4to, 1873.

[145]

Loc. cit.

[146]

References to these works are given on p. [101].

[147]

Zitschr. wiss. Zool. Bd. xli. 1885, p. 48.

[148]

Nature, vol. xlvi. 1892, p. 611.

[149]

Zool. Anz. vol. xv. 1892, p. 64.

[150]

Zeitschr. wiss. Zool. Bd. lix. 1895, p. 83.

[151]

Arb. Inst. Würzburg, Bd. iv. 1877-1878, p. 305.

[152]

Journ. Mar. Biol. Ass. vol. iii. 1893-1895, p. 22.

[153]

Quart. J. Micr. Sci. vol. xxiii. 1883, p. 349; Ibid. vol. xxvii. 1887, p. 605.

[154]

Cf. Willey, Amphioxus and the Ancestry of the Vertebrates, Macmillan, 1894.

[155]

Ann. Sci. nat. 7, sér. vol. xiii. 1892, p. 321.

[156]

E. Rohde, SB. Ak. Berlin, 1892, p. 515.

[157]

R. Hesse, Zeitschr. wiss. Zool. Bd. liv. 1892, p. 548.

[158]

E. Rohde, Zool. Beitr. Bd. i. 1885, p. 11.

[159]

E. Rohde, Zool. Anz. xvii. 1894, p. 38.

[160]

Monographie der Nematoden, 4to, Berlin, 1866.

[161]

Zeit. Physiol. Chem. vol. xiv. 1890, p. 318.

[162]

N. A. Cobb, P. Linn. Soc. N.S. Wales, 2nd ser. vol. vi. 1891, p. 143.

[163]

Monographie der Nematoden, Berlin, 1866, p. 192.

[164]

Zool. Anz. vol. xvi. 1893, p. 432.

[165]

Arch. Naturg. 60 Jahrg. Bd. i. 1894, p. 255.

[166]

SB. Ak. Berlin, 1891, p. 57.

[167]

[Hamann subsequently withdrew these statements.]

[168]

Leuckart, The Parasites of Man, English Trans. by W. E. Hoyle, Edinburgh, 1886, p. 56.

[169]

O. Bütschli, Zeitschr. wiss. Zool. Bd. xxvi. 1876, p. 103.

[170]

O. Hamann, Centrlb. Bakter. vol. xi. 1892, p. 501.

[171]

Zeitschr. wiss. Zool. vol. xxiii. 1873, p. 402.

[172]

Ibid. vol. xlii. 1885, p. 708.

[173]

Ann. Nat. Hist. 5th ser. vol. ix. 1882, p. 301.

[174]

Macleay Memorial Volume, Sydney, 1893, p. 252; and Proc. Linn. Soc. N.S.W. 2nd ser. vol. v. 1890, p. 449.

[175]

4th edition, 1880.

[176]

Compendium der Helminthologie, Hannover, 1878, and Nachtrag, 1889.

[177]

A. Heller, "Darmschmarotzen" in v. Liemssen's Handb. d. sp. Path. u. Ther. vol. vii.

[178]

Cobbold's Parasites, London, 1879, p. 246.

[179]

Arch. Zool. exper. 1 sér. tom. vii. 1878, p. 283.

[180]

Arch. Zool. exper. 1 sér. tom. vii. 1878, p. 283.

[181]

Balbiani, Anat. Physiol. 7th year, 1870-71, p. 180.

[182]

A Treatise on Parasites and Parasitic Diseases. English Trans. by G. Fleming, London, 1892.

[183]

Journ. Roy. Agric. Soc. 3rd series, vol. iv. 1893.

[184]

Sci. Mem. Medic. Officers, Army of India, vol. vii. 1892, p. 51.

[185]

Shipley, Proc. Phil. Soc. Camb. vol. viii. 1892-95, p. 211.

[186]

"The Distribution, etc., of Filaria sanguinis hominis," Trans. of 7th Inter. Congress of Hygiene, vol. i. 1892, p. 79.

[187]

v. Linstow, Arch. mikr. Anat. vol. xl. 1892, p. 498.

[188]

zur Strassen, Zeitschr. wiss. Zool. vol. liv. 1892, p. 655.

[189]

Rud. Leuckart, Abh. Sachs. Ges. vol. xiii. 1887, p. 567.

[190]

Macleay Memorial Vol. Sydney, 1893, p. 253.

[191]

Centrbl. Bakter. vol. viii. 1890, p. 489.

[192]

J. Percival, Nat. Sci. vol. vi. 1895, p. 187.

[193]

A. Strubell, Bibl. Zool. Bd. i. Heft 2, 1888, p. 1.

[194]

C. R. Ac. Sci. cxviii. 1894, p. 549.

[195]

Bihang Svenska Ak. Handl. viii. No. 11, 1883.

[196]

Anat. Untersuch. ü. freilebende Nordsee-Nematoden, Leipzig, 1886.

[197]

Cobb, P. Linn. Soc. N. S. Wales, 2nd ser. viii. 1893, p. 389.

[198]

Zeitschr. wiss. Zool. Bd. xvii. 1867, p. 539.

[199]

Panceri, Atti Acc. Napoli, vii. 1878, No. 10.

[200]

Panceri, Atti Acc. Napoli, vii. 1878, No. 10.

[201]

Arch. Naturg. 35 (i.), 1869, p. 112.

[202]

Zeitschr. wiss. Zool. Bd. xlii. 1885, p. 708.

[203]

Arch. Naturg. Jahrg. iii. Bd. i. 1837, p. 52; and van Beneden, Animal Parasites, p. 91. International Sci. Series.

[204]

F. Vejdovsky, Zeitschr. wiss. Zool. Bd. xliii. 1886, p. 369; Zeitschr. wiss. Zool. Bd. xlix. 1888, p. 188.

[205]

Arch. mikr. Anat. Bd. xxxvii. 1891, p. 239.

[206]

Arch. mikr. Anat. Bd. xxxiv. 1889, p. 248.

[207]

A. E. Verrill, P. U. S. Mus. vol. ii. 1879, p. 165.

[208]

O. Bürger, Zool. Jahrb. Anat. Bd. iv. 1891, p. 631.

[209]

H. B. Ward, Bull. Mus. Harvard, vol. xxiii. 1892-93, p. 135.

[210]

Mem. Acc. Torino, 2nd ser. vol. xl. 1890, p. 1.

[211]

Centrlb. Bakter. Bd. ix. 1891, p. 760.

[212]

Zeitschr. wiss. Zool. Bd. vii. 1856, p. 1.

[213]

Zool. Anz. vol. x. 1887, p. 602.

[214]

Von Linstow, Hannover, 1878, and Nachtrag, 1889.

[215]

H. B. Ward, P. Amer. Ac. new ser. vol. xix. 1892, p. 260.

[216]

Jen. Zeitschr. Bd. xxv. 1891, p. 113.

[217]

Bibl. Zool. Bd. ii. Heft 7. 1893.

[218]

Jen. Zeitschr. Bd. xxv. 1891, p. 113.

[219]

Zool. Anz. Bd. xv. 1892, p. 195.

[220]

Zool. Anz. vol. xv. 1892, p. 52.

[221]

Zool. Anz. vol. viii. 1885, p. 19.

[222]

Shipley, Quart. J. Micr. Sci. vol. xxxix. 1896.

[223]

O. Hertwig, Jen. Zeitschr. Bd. xiv. 1880, p. 196.

[224]

P. Gourret, Ann. Mus. Marseille, tom. ii. Mem. 2, 1884, p. 103.

[225]

Bibl. Zool. vol. i. 1888-89, p. 1.

[226]

Scott, Annals of Scottish Natural History, 1892 and 1893.

[227]

E. Béraneck, Rev. Zool. Suisse, vol. iii. 1895, p. 137.

[228]

Ann. Mag. Nat. Hist. 6th ser. vol. xiii. 1894, p. 440.

[229]

Archiv Naturg. 58 Jahrg. Bd. i. 1892, p. 333.

[230]

I Chetognati, Flora u. Fauna d. Golfes von Neapel, Mon. v. 1883.

[231]

loc. cit.

[232]

loc. cit.

[233]

The Rotifera, two vols, and supplt. London, 1886-89.

[234]

Phil. Trans. vol. xix. No. 220, p. 254 (abridged ed. vol. iii. 1705, p. 651).

[235]

Ibid. vol. xxiii. No. 283, p. 1304 (abridged ed. vol. v. p. 6).

[236]

Ibid. vol. xxiii. No. 295, p. 1784 (abridged ed. vol. v. p. 175).

[237]

Ibid. No. 337, vol. xxviii. 1714, p. 160.

[238]

Employment for the Microscope. London, 1785.

[239]

Paris, 1841.

[240]

Quart. Journ. Micr. Sci. vol. i. 1853, pp. 3-8, 65-76.

[241]

Trans. Micr. Soc. London, vol. i. (n.s.), 1853, pp. 1-19.

[242]

Verh. Ges. Würzb. vol. iv. 1854; Zeitschr. wiss. Zool. vols. iii. vi. 1851-55.

[243]

Zeitschr. wiss. Zool. vols. vii. ix. xii. 1856-58-63.

[244]

London, 1861.

[245]

Zeitschr. wiss. Zool. vol. xxxix. 1883.

[246]

Ann. Nat. Hist. ser. 6, vol. v. 1890, p. 1; viii. 1891, p. 34.

[247]

Jen. Zeitschr. Nat. vol. xix. 1886; and Zeitschr. wiss. Zool. vols. xliii. xlix. 1886-90.

[248]

Zeitschr. wiss. Zool. vol. xliv. 1886, p. 273.

[249]

Ibid. vol. xliv. p. 396; xlvii. 1888, p. 353; liii. 1892, p. 1.

[250]

For additions see Rousselet, J. Roy. Micr. Soc. 1893 and 1897.

[251]

See p. [228].

[252]

Quart. Journ. Micr. Soc. (n.s.) vol. xxiv. 1884, p. 352.

[253]

The definition of the Orders and systematic position of the genera and species referred to under this head will be found in a following section (pp. [220] f.).

[254]

Reprinted in Baker's Employment for the Microscope, 1785, pp. 267 f.

[255]

"Wheel Animals, though found with most Certainty in Leaden Gutters, etc. are often discovered in the Waters of some Ditches, and likewise in Water that has stood a considerable Time even in the House; for I have often met with them, in sufficient Plenty, in a Sort of slimy Matter that is apt to be produced on the Sides of Glasses and other Vessels, that are kept long with the Infusions of Hay or other Vegetables; and probably they are wafted thither by the Air, when in the Condition of little dry Globules."

[256]

Gosse's account of the "Structure, Functions, and Homologies of the Manducatory Organs in the Class Rotifera" (in Phil. Trans. 1856) remains as the most complete anatomical account we have, though his attempt to identify these parts with the modified limbs of the Arthropod mouth has met with no support from subsequent workers. Gosse rendered these parts clearly visible by the use of dilute caustic alkali.

[257]

A modification of this type is seen in the parasite Drilophagus, where the unci and rami are two-pronged at the end, but the trophi are not movable on one another, but protrusible as a whole to serve as an organ of attachment to the Oligochaete Lumbriculus, to which this Rotifer attaches itself. See Vejdovsky, "Ueb. Drilophaga bucephalus," etc., in SB. Böhm. Ges. Jahrg. 1882 (1883), p. 390.

[258]

"Zur Rotatorien Württemburgs," in Jahresb. Ver. Würt. vol. l. 1894, p. 57.

[259]

Similarly Hudson and Zelinka both regard the dorsal antenna as formed by the coalescence of two antennae. These retain their distinctness in Asplanchna; in some Bdelloida the single antenna is supplied by a pair of nerves.

[260]

C. R. Ac. Sci. cxi. 1890, p. 310; cxiii. 1891, p. 388.

[261]

Acta Univ. Lund. xxviii. 1891-92.

[262]

[See, however, Calman, Natural Science, xiii. 1898, p. 43.]

[263]

Zeitschr. wiss. Zool. xxii. 1872, p. 455.

[264]

Arch. Zool. Exp. sér. 2, i. 1883, p. 131.

[265]

Zeitschr. wiss. Zool. xliv. 1886, p. 273.

[266]

Ibid. liii. 1892, p. 1.

[267]

[See further Jennings, Bull. Mus. Harvard, xxx. 1896, p. 1; Erlanger and Lauterborn, Zool. Anz. xx. 1897, p, 452; and Lenssen, Zool. Anz. xxi. 1898, p. 617.]

[268]

It does not appear to us that Zelinka is justified by his account of the development in regarding this cup as other than a part of the disc.

[269]

The classification we have adopted is a modification of that made by Hudson and Gosse; we have divided up their first Order Rhizota into two, and split off from Flosculariidae the family Apsilidae; removed the Asplanchnaceae from the admittedly heterogeneous Order Ploima, made distinct families in the Ploima for Microcodonidae and Rhinopidae, and created a third new Order for the Seisonaceae. Ehrenberg, Gosse, and Hudson, being the authors of most of the genera, are designated by their initials only.

[270]

This second species has also been found in the Northern United States.

[271]

This Order has been monographed recently by Janson in Abh. Ver. Brem. Bd. xii. Beilage, 1893, p. 1.

[272]

See Hudson in Month. Micr. Journ. vol. vi. 1871, pp. 121, 215, and Quart. Journ. Micr. Sci. (n.s.) xii. 1872, p. 333; Lankester, ibid. p. 338; Levander in Act. Soc. Faun. Fenn. xi. 1894.

[273]

In Denk. Ak. Wien, vol. vii. 1854, 2 Abth., p. 15. As has been suggested by Deby and by Daday, it is not impossible that Hexarthra is identical with Pedalion (and in this case the latter name, as newer, should be suppressed in favour of the former); but we must suppose that Schmarda's figure of the front view is a combination, more or less from memory or notes, of two sketches or notes taken some time before publication; the one a side view somewhat obliquely flattened, showing the two eyes as in Levander's Fig. 3; the other a front view, showing the two pairs of lateral limbs in their correct positions under pressure.

[274]

The male of Rhinops vitrea is exceptional in possessing a complete, functional alimentary canal, with mastax, stomach, and intestine (Rousselet). That of Proales werneckii has a mastax, but no intestine (Rothert).

[275]

For a full account of this group see Claus in Festschr. Z.-B. Ges. Wien, 1876, p. 75; and Plate in Mt. Stat. Neapel, vol. vii. 1886-87, p. 234; Ann. Nat. Hist. ser. 6, vol. ii., 1888, p. 86.

[276]

[Eighteen more have since been recorded.]

[277]

I have recently found a large species of this genus dwelling in the shell of the large Cladoceran Crustacean, Eurycercus lamellatus. It is remarkable for its power of completely telescoping its extremities within the middle segments, and for its immense foot-glands, both characters being doubtless correlated with its habitat. Rousselet identifies it with P. petromyzon.

[278]

Month. Micr. Journ. vol. ix. 1873, p. 287; Journ. Quekett Club, ser. 2, vol. ii. 1884-86, p. 231.

[279]

See Dr. Hudson's very suggestive presidential addresses to the Royal Microscopical Society, published in their Journal, vols. ix.-xi. 1889-91.

[280]

Euchlanis lynceus.—This is clearly not an Euchlanis, and of the six names referred to—Ploesoma, Gomphogaster, Gastropus, Gastroschiza, Bipalpus, and Dictyoderma—the first has priority, and the other five drop by the laws of zoological nomenclature.

[281]

Journ. Quekett Club, ser. 2, vol. v. 1892-94, p. 205.

[282]

Trans. Micr. Soc. (n.s.) i. 1853, p. 18 (read Dec. 31, 1851): "We may say, therefore, that the Rotifera are organized upon the plan of an Annelid larva.... I do not hesitate to draw the conclusion ... that the Rotifera are the permanent forms of Echinoderm larvae, and hold the same relation to the Echinoderms that the Hydriform Polypi hold to the Medusae, or that Appendicularia holds to the Ascidians."

[283]

Quart. Journ. Micr. Sci. (n.s.) vol. xvii. 1877, p. 399.

[284]

Ibid. (n.s.) vol. xx. 1880, p. 381.

[285]

Arb. Z. Inst. Wien, vols. i. iii. v. 1878-84; Lehrbuch der Zoologie, part iii. 1891.

[286]

Zeitschr. wiss. Zool. vol. xliv. 1886, p. 1.

[287]

The Microscope (Detroit), 1887-88.

[288]

Zeitschr. wiss. Zool. xlix. 1890, p. 209.

[289]

Ann. Sci. Nat. ser. 3, vol. xv. 1851, p. 158.

[290]

Zeitschr. wiss. Zool. vol. xlv. 1887, pp. 401-467, t. xx-xxii.

[291]

The breadth of the latter is estimated from Reinhard's figure.

[292]

The Echiuroid Gephyrea (see p. [434]) are by some authorities considered to be a division of the Chaetopoda.

[293]

Another worm, Histriobdella (Histriodrilus) homari, which is parasitic on the eggs of the lobster, and which occurs on our coast, has been placed amongst the Archiannelida. It is a minute form, with peculiarities in its anatomy which render its affinities uncertain.

[294]

Quart. J. Micr. Sci. xxvii. 1887, p. 109.

[295]

J. Mar. Biol. Assoc. vol. i. (n.s.) 1889-90, p. 119.

[296]

Schimkewitsch, Zeitschr. f. wiss. Zool. lix. 1895, p. 46.

[297]

Hatschek, Arb. Zool. Inst. Wien, iii. 1881, p. 79.

[298]

Fraipont, "Le Genre Polygordius," Fauna u. Flora des Golfes v. Neapel, Monogr. xiv. 1887.

[299]

T. J. Parker, Lessons in Elementary Biology, London, 1891, p. 267, gives a full account of the anatomy and development of Polygordius.

[300]

"Die Capitelliden," Fauna u. Flora d. Golfes v. Neapel, Monogr. xvi. 1887, p. 350.

[301]

Encyclopaedia Britannica, 9th ed., Art. "Mollusca," p. 652.

[302]

Benham, "The Post-Larval Stage of Arenicola," J. Mar. Biol. Assoc. iii. (n.s.) 1893, p. 48.

[303]

The blood is colourless in Syllidae and Nephthydidae.

[304]

Ehlers states that some Eunicidae have green blood.

[305]

Benham, Quart. J. Micr. Sci. xxxix. 1896, p. 1.

[306]

Schaeppi, Jena. Zeit. xxviii. 1894, p. 217.

[307]

Goodrich, Quart. J. Micr. Sci. xxxiv. 1893, p. 387.

[308]

Benham, Quart. J. Micr. Sci. xxxii. 1891, p. 325. See also Bourne (nephridium of Polynoë), Tr. Linn. Soc. (Zool.), ii. 1883, p. 357; Meyer, for nephridium of Terebellidae, Sabellidae, and Cirratulidae, in Mt. Zool. Stat. Neapel, vii. 1887, p. 592.

[309]

It is worthy of note that in Aeolosoma alone amongst the Oligochaeta does the brain lie in the prostomium in the adult.

[310]

Andrews, "The Eyes of Polychaetes," J. Morph. vii. 1892, p. 169.

[311]

Wistinghausen, "Entwick. v. N. dumerilii," Mt. Zool. Stat. Neapel, x. 1891, p. 41.

[312]

This is a modification of the classification proposed by me at the meeting of the British Association at Oxford, 1894 (see Report, p. 696). For further characteristics of these Orders and sub-Orders see below Chap. XII. Ehlers, "Die Borstenwürmer," 1864, gives a historical survey of the group, and enumerates the earlier classifications.

[313]

In Coabangia (see p. [284]) the anus is near the anterior end, on the ventral surface.

[314]

It is doubtful whether these organs are palps or only lateral lips.

[315]

Pruvot traced the nerve supply to these organs, and thus established their homology. Arch. d. Zool. Expér. (ser. 2) iii. 1885, p. 211.

[316]

Meyer, "Stud. ub. d. Körperbau der Anneliden," Mt. Zool. Stat. Neapel, vii. 1887, p. 592; viii. 1888, p. 462. In this work a great number of important and interesting anatomical facts are recorded with respect to the Terebelliformia and Sabelliformia, as well as certain details as to the structure and development of the nephridia.

[317]

In some of the members of this family paired lateral tentacles appear to exist.

[318]

It is possible that some of these may be peristomial.

[319]

Individual cases in which chaetae are present have been recorded.

[320]

Meyer, loc. cit.

[321]

Haswell, P. Linn. Soc. N.S. Wales, vii. 1883, p. 251.

[322]

Eisig, "Die Capitelliden," Fauna u. Flora G. v. Neapel, Monogr. xvi. 1887, p. 331.

[323]

Compare with this the muscular organ of Dinophilus, p. [243], Protodrilus, and a similar structure which occurs in Terebellids.

[324]

Korschelt, "Über Ophryotrocha puerilis," Zeitschr. f. wiss. Zool. lv. 1893, p. 224.

[325]

Eisig, Mt. Zool. Stat. Neapel, ii. 1881, p. 255.

[326]

They are specially large also in the Typhloscolecidae; while Racovitza (Ann. Mag. N. H. (ser. 6), xv. 1895, p. 279) has recently suggested that the caruncle of Amphinomidae belongs to the category of nuchal organs, and compares it with the ciliated lappets of Pterosyllis.

[327]

Ehlers, Zeitschr. f. wiss. Zool. liii. 1892, p. 217.

[328]

See Claparède and Metschnikoff, "Beit. zur Kennt. d. Entwick der Chaetopoden," Zeitschr. f. wiss. Zool. xix. 1869, p. 163; and Fewkes, "On the Development of certain Worm Larvae," Bulletin Mus. Harvard, xi. 1883, p. 167.

[329]

For an account of the anatomy and development of a Trochosphere, see Hatschek, on Eupomatus, in Arbeit. Zool. Inst. Wien, vi. 1885. Also Meyer, Mt. Zool. Stat. Neapel, viii. 1888, p. 462; and for Polynoid larva see Häcker, Zool. Jahrb. Abth. Anat. viii. 1895, p. 245.

[330]

See Meyer (ref. on p. [261]).

[331]

Many of the Polynoids are sexually dimorphic.

[332]

Claparède, "Annélides Chétopodes du Golfe de Naples," Supplement, 1870; and Wistinghausen, Mt. Zool. Stat. Neapel, x. 1891, p. 41.

[333]

Claparède used the term "epigamous" for this phase; Ehlers employed the term "epitokous," whilst he called the "Nereid" phase "atokous," under the impression that the worm did not become mature in this condition.

[334]

Malaquin gives a detailed account of the asexual reproduction in Syllidae in Recherches sur les Syllidiens, Lille, 1893, and in Revue Biol. d. Nord de la France, iii. 1891. See also St. Joseph, "Les annelides polychétes des côtes de Dinard," Ann. Sci. Nat. Zool. (7th ser.) i. 1886, p. 134.

[335]

Alex. Agassiz, Boston J. Nat. Hist. vii. 1863, p. 384.

[336]

Huxley, Edinb. New Philosoph. Journ. 1855, i. p. 113.

[337]

"Challenger" Reports, vol. xii. 1885, "Polychaeta," p. 198; and Oka, Zoolog. Centralbl. ii. 1895, p. 591.

[338]

Two new heads have been observed in Typosyllis variegata by Langerhans, and two new tails in another Syllis.

[339]

Dalyell, The Powers of the Creator revealed, etc., vol. ii. 1853, p. 225 et seq.

[340]

von Kennel, Arb. Zool. Instit. Würzburg, vi. 1883, p. 259.

[341]

Leidy, Proc. Acad. Nat. Hist. Philadelphia, 1883, p. 204.

[342]

Giard, C. R. Soc. Biol. v. 1893, p. 473.

[343]

See M‘Intosh, Ann. Mag. Nat. Hist. (ser. 4) ii. 1868, p. 276.

[344]

Lankester has suggested that a strong acid is secreted for the purpose, see Ann. Mag. Nat. Hist. (ser. 4) i. 1868, p. 233.

[345]

M‘Intosh, Ann. Mag. Nat. Hist. (ser. 6) xiii. 1894, p. 1.

[346]

Dalyell, The Powers of the Creator revealed, ii. 1853, p. 217.

[347]

Watson, Journ. R. Mic. Soc. 1890, p. 685; see also Dalyell, loc. cit. ii. p. 195.

[348]

Schmiedeberg, Mt. Zool. Stat. Neapel, iii. 1882, p. 373.

[349]

For pelagic forms, see Camille Viguier, Arch. de Zool. Expér. (ser. 2) iv. 1886, p. 347; also Reibisch, Die pelag. Phyllodociden u. Typhloscoleciden d. Plankton Exped. 1895.

[350]

Lankester, Journ. Anat. and Physiol. 1868, p. 114; and 1870, p. 119; see also MacMunn, "On the Chromatology of the Blood in some Invertebrates," Quart. J. Micr. Sci. xxv. 1885, p. 469.

[351]

For coloured pictures of worms consult Schmarda, "Neue wirbellose Thiere," 2nd part, 1861; Milne Edwards in Cuvier's "Règne Animal" (Ed. Disciples de Cuvier).

[352]

Semper, Animal Life, "Internat. Sci. Series," 1881, p. 401.

[353]

The experiments were made by Mr. Garstang at the Laboratory of the Marine Biological Association, and are recorded by Poulton in The Colours of Animals, "Internat. Sci. Series," 1890, p. 201.

[354]

Panceri, Atti Acad. Sci. Napoli, vii. 1875.

[355]

M‘Intosh, H.M.S. "Challenger" Reports, "Polychaeta," vol. xii. p. ix.

[356]

For an account of these worms see M‘Intosh, loc. cit. p. 257.

[357]

For a list of parasitic Polychaetes see St. Joseph, Ann. Sci. Nat. (ser. 7) v. 1888, p. 141.

[358]

Semper, loc. cit. p. 340.

[359]

See "Challenger Reports," and St. Joseph, loc. cit.

[360]

"Challenger" Reports, loc. cit. p. xxx.

[361]

See Hornell, Fauna of Liverpool Bay, Report III. 1892, p. 126.

[362]

Zittel, Handbuch d. Palaeontologic (Palaeozoologie), i. 1876-80, p. 562.

[363]

Ehlers, Zeitschr. f. wiss. Zool. xviii. 1868, p. 241.

[364]

The Chaetopteridae may have to be placed elsewhere in the system, as they are peculiarly modified, and present features recalling the Cryptocephala, from which it is possible they have descended.

[365]

Meyer (Mt. Zool. Stat. Neapel, vii. 1887, p. 669, note) suggests that the tentacular filaments of Cirratulids are really prostomial, but have shifted back on to the peristomium, or even farther.

[366]

It is probable that the genital ducts of Sternaspis and Chlorhaemids are modified nephridia.

[367]

The character of head and parapodium in each family will be gathered from the figures accompanying the general description in Chap. X., so that detailed description is unnecessary. In all cases the chaetae form valuable specific characters.

The examples of the various families are British, unless the opposite is expressly stated; but most of them are not confined to our shores, and the foreign localities are usually given. No attempt is made to enumerate all the British species.

The following books may be found useful for identifying the worms:—

Claparède, Recherches anat. sur les Annélides observées dans les Hebrides, 1861; Annélides Chétopodes du golfe de Naples, 1868, and Suppl., 1870.

Cunningham and Ramage, "Polychaeta Sedentaria of the Firth of Forth," Trans. Roy. Soc. Edinburgh, xxxiii. 1888, p. 635.

Ehlers, Die Borstenwürmer, 1868.

Johnston, "British Museum Catalogue of Non-Parasitical Worms," 1865.

M‘Intosh, "British Annelida," Trans. Zool. Soc. ix. 1877, p. 371; "Invert. Marine Fauna of St. Andrews; Annelida," Ann. Mag. Nat. Hist. (4) xiv. 1874, p. 144.

Malmgren, "Nordiska Hafs-Annulater," Öfversigt af K. Vet.-Akad. Förhandlingar, 1865, pp. 51, 181, 355; and "Annulata Polychaeta," ibid. 1867, p. 127.

St. Joseph, "Les Annélides Polychétes des côtes de Dinard," Ann. Sci. Nat. (Zool.) (7) vol. i. 1886, p. 127; v. 1888, p. 141; xvii. 1894, p. 1; xx. 1895, p. 185.

[368]

Malaquin, Recherches sur les Syllidiens, 1893; for structure of the gizzard, see also Haswell, Quart. J. Micr. Sci. xxvi. 1886, p. 471; and xxx. 1889, p. 31.

[369]

See M‘Intosh's Memoirs, loc. cit.

[370]

Herein are included the various genera formed by Kinberg, Malmgren, and others.

[371]

It appears to be the same as P. grubiana Clap.

[372]

Marenzeller has shown that Johnston's P. scolopendrina is not identical with that of Savigny, and suggests the above name for it.

[373]

F. Buchanan, "Report on Polychaetes, Part I." Sci. Proc. Roy. Dublin Soc. vii. (n.s.) 1893, p. 169.

[374]

Polyodontes Ran. deserves mention as being a large, rare form with peculiar pedal gland; cf. Eisig (ref. on p. [268]), p. 324; and Buchanan, Quart. J. Micr. Sc. xxxv. 1894, p. 433.

[375]

Many authorities regard this species as synonymous with Savigny's P. laminosa.

[376]

According to a verbal communication from Mr. J. Hornell of Jersey, they belong to P. maculata Müll., while Mr. Garstang believes them to belong to Eulalia viridis.

[377]

These segmentally-arranged brown spots may perhaps be photogenic.

[378]

Greef, Acta Ac. German., xxxix. 1877.

[379]

Greef, Zeitschr. f. wiss. Zool. xlii. 1885, p. 432.

[380]

Buchanan, Quart. J. Micr. Sci. xxxv. 1894, p. 445.

[381]

Buchanan, Sci. Proc. R. Dublin Soc. viii. (n.s.) 1893, p. 169.

[382]

Reibisch, Phyllodociden u. Typhloscoleciden d. Plankton Exped. 1895.

[383]

The British species is usually referred to as C. insignis Baird, but Joyeux Laffuie (Arch. Zool. Exp. (ser. 2) viii. 1890, p. 244) has shown that there is only one European species. It is possible that there is a closer affinity with the Sabelliformia than is at present supposed.

[384]

Compare Sternaspis, p. 336.

[385]

For literature, see Benham, Quart. J. Micr. Sci. xxxix. part 1, 1896, p. 1.

[386]

F. Buchanan, Quart. J. Micr. Sci. xxxi. 1890, p. 175.

[387]

In some genera there are no gills, e.g. Leaena.

[388]

These characters are not necessarily generic.

[389]

Eisig, "Die Capitelliden," Fauna u. Flora G. v. Neapel, Monogr. xvi. 1887.

[390]

Ed. Meyer., Arch. mikr. Anat. xxi. 1882, p. 769.

[391]

Vejdovsky, Denk. Akad. Wien, xliii. 1882, part 2, p. 33; and Rietsch, Ann. Sci. Nat. (Zool.) ser. 6, xiii. 1882, art. 5.

[392]

For anatomy see Meyer, Mt. Zool. Stat. Neapel, vii. 1887.

[393]

Andrews, Journ. Morph. v. 1891, p. 271.

[394]

A. G. Bourne, Quart. J. Micr. Sci. xxiii. 1883, p. 168.

[395]

Closely allied is Manayunkia Leidy, which occurs in fresh-water lakes of America. Another fresh-water genus is Coabangia Giard, which perhaps deserves the creation of a special family. The anus is ventral and anterior. The chaetae are peculiarly arranged, dorsal uncini being present only on four segments. The first body segment carries a ventral bundle of five great "palmate" chaetae.

[396]

For the anatomy see Meyer, Mt. Stat. Neapel, vii. 1887; see also above, p. 306.

[397]

von Graff, "Myzostomida," "Challenger" Reports, part 27, vol. x. 1884; and "Supplement," part 61, vol. xx. 1887.

[398]

Marenzeller, Anz. Akad. Wien, xxxii. p. 192.

[399]

Mt. Zool. Stat. Neapel, xii. 1896, p. 227; where, too, see literature.

[400]

Beard, Mt. Zool. St. Neap. v. 1884, p. 544.

[401]

Quart. J. Micr. Sci. (n.s.) vol. iv. 1864, p. 258; and v. pp. 7, 99.

[402]

Zeitschr. wiss. Zool. xix. 1869, p. 563.

[403]

De Lumbrici terrestris Historia naturali, Brussels, 1829.

[404]

Naturg. ein. Wurm-Arten d. süssen u. salzigen Wasser, Copenhagen, 1771.

[405]

Trans. Roy. Soc. Victoria, vol. i. 1888, p. 1.

[406]

Phil. Trans. clxxxvi. 1895, A, p. 383.

[407]

Mém. cour. Ac. Belg. lii. 1890-93.

[408]

Quart. J. Micr. Sci. xxxi. 1890, p. 83.

[409]

Beddard, Ibid. xxxiii. 1892, p. 325.

[410]

Beddard, Ann. Mag. Nat. Hist. (6) xiii. 1894, p. 205.

[411]

Mém. Soc. Zool. France, iii. 1890, p. 223.

[412]

Vegetable Mould and Earthworms, London, 1881.

[413]

Zool. Anz. xi. 1888, p. 72.

[414]

See Fletcher, P. Linn. Soc. N.S.W. (2) iii. 1889, p. 1542.

[415]

In Sitzungs-Ber. Böhm. Ges. 1889, p. 183.

[416]

See Dr. Rosa in Ann. Hofmus. Wien, vi. 1891, p. 379.

[417]

Entwickelungsgeschichtliche Untersuchungen, Prag, Heft i. 1888, p. 33.

[418]

See Kleinenberg, Quart. J. Micr. Sci. xix., 1879, p. 206.

[419]

Both Col. Feilden and Mr. Trevor-Battye found specimens in Kolguiev.

[420]

Neue wirbellose Thiere, Leipzig, ii. 1861, p. 11.

[421]

Kew Bull. Misc. Information, No. 46, 1890.

[422]

Rev. Biol. Nord France, i. 1889, p. 197.

[423]

SB. Ges. naturf. Berlin, 1893, p. 19.

[424]

System u. Morph. d. Oligochaeten, Prag, 1884.

[425]

See my text-book of Zoogeography (Cambridge, 1895) for fuller treatment.

[426]

Ann. Mag. Nat. Hist. (6) ix. 1892, p. 12.

[427]

Darwin, Vegetable Mould and Earthworms, p. 121.

[428]

"An Attempt to classify Earthworms," Quart. J. Micr. Sci. xxxi. 1890, p. 201.

[429]

Oxford, 1895.

[430]

See especially Vejdovsky, Syst. u. Morph. Olig. Prag, 1884.

[431]

Vejdovsky, Monographie der Enchytraeiden, Prag, 1879. Michaelsen, "Synopsis der Enchytraiden," Abh. Ver. Hamburg, xi. 1889, p. 1.

[432]

J. P. Moore, "The Anatomy of Bdellodrilus," J. Morphol. x. 1895, p. 497.

[433]

Beddard, Trans. Roy. Soc. Edin. xxxv. 1890, p. 629, and xxxvi. 1892, p. 1.

[434]

A. G. Bourne, "On the Naidiform Oligochaeta," Quart. J. Micr. Sci. xxxii. 1891, p. 335.

[435]

F. E. Beddard, Trans. Roy. Soc. Edin. xxxvi. 1892, p. 273.

[436]

Vejdovsky, System u. Morph. d. Oligochaeten, Prag, 1884.

[437]

"Anatomical Notes on Sutroa," Zoe. ii. 1892, p. 321.

[438]

"Pacific Coast Oligochaeta," Mem. California Acad. Sci. vol. ii.

[439]

Quart. J. Micr. Sci. xxxvi. 1894, p. 307.

[440]

See Spencer, Proc. Roy. Soc. Vict. v. 1893, and Fletcher, P. Linn. Soc. N.S.W. 1886-1888, for Australian forms; Rosa, Ann. Mus. civ. Genova, vi. 1886, x. 1890, and xii. 1892, for Oriental species, etc.

[441]

See Fletcher and Spencer, already quoted, for Australian species.

[442]

Eisen, "Anat. Studies on Ocnerodrilus," Proc. Calif. Acad. (2) iii. 1892, p. 228.

[443]

Beddard, Ann. Mag. Nat. Hist. (6) x. 1892, p. 74.

[444]

Beddard, P. Z. S. 1885 and 1895, for Antarctic Acanthodrilids; Michaelsen, in Jahrb. Hamburg. Anst. 1888-95, for Benhamia.

[445]

For a general account of the Eudrilidae, see my Monograph of the Order Oligochaeta, Oxford, 1895.

[446]

Nouv. Arch. Mus. Paris, viii. 1872, p. 5.

[447]

The scattered literature of this family is due to Benham, Michaelsen, Perrier, Rosa, and others.

[448]

Rosa, "Revisione dei Lumbricidae," Mem. Acc. Torino (2), xliii. 1893, p. 399; also the Rev. H. Friend's numerous and useful papers, and especially "A New Species of Earthworms," Proc. Roy. Irish Ac. (3) ii. 1891-93, p. 402; and "The Earthworms of Ireland," Irish Nat. v. 1896, p. 69, etc.

[449]

In the tables the figures refer to the segments of the body. Opposite the name of each species are two sets of lines; the upper series indicate the segments occupied by the clitellum; the lower series those occupied by the tubercula pubertatis. The dots indicate the occasional extension of the clitellum or of the tubercula.

[450]

"Annelés," vol. iii. 1889-90, p. 477, in the Suites à Buffon.

[451]

See v. Kennel, Zool. Jahrb. ii. 1887, p. 37.

[452]

Nouvelle Monographie des Sangsues médicinales. Paris, 1857.

[453]

Quart. J. Micr. Sci. xxvi. 1886, p. 317.

[454]

See Grube, "Annulaten" of Middendorff's Sibirische Reise, Zoology, 1851, p. 20; and Kowalevsky, Bull. Ac. St. Petersb. v. June 1896.

[455]

See ref. on p. [395].

[456]

Asajiro Oka, Zeitschr. wiss. Zool. lviii. 1894, p. 79.

[457]

See Bürger, quoted on p. [403].

[458]

Loc. cit.

[459]

Quart. J. Micr. Sci. xxiv. 1884, p. 419; see also ibid. xxxiv. 1893, p. 545, which is mainly a criticism of Bolsius' additions to the very considerable literature upon the Leech nephridium.

[460]

"Spermatophores as a Means of Hypodermic Impregnation," J. Morphol. iv. 1891, p. 361.

[461]

Zeitschr. wiss. Zool. lviii. 1894, p. 440; and Zool. Jahrb. Anat. iv. 1891, p. 697.

[462]

"Annelés," vol. iii. 1889-90, p. 493, in the Suites à Buffon.

[463]

Whitman quotes with regretful approval (Proc. Americ. Acad. xx. 1884-85, p. 76) Sir J. Dalyell's remark, "It does not appear that the history of the leech has advanced in proportion to the number of literati who have rendered it the subject of discussion," and adds on his own account the following severe indictment of his predecessors: "As a considerable share of the work done in this direction is purely systematic, it is somewhat surprising that not a single description of any Hirudo has been given with sufficient accuracy and completeness for a close comparison of even its more important external characters with those of other species."

[464]

"Hirudinées de l'Italie," etc., Boll. Mus. Zool. Torino, vol. ix. 1894, No. 192. See also Apathy, "Süsswasser-Hirudineen," Zool. Jahrb. Syst. iii. 1888, p. 725.

[465]

Zeitschr. f. die gesammt. Naturwiss. vi. 1872, p. 422.

[466]

But Pennant in his British Zoology has referred to a leech which is even larger. Upon the huge Basking shark (Selache) the fishermen sometimes observe a leech, which invariably drops off when the fish is brought to the surface, "of a reddish colour and about 2 feet in length"; this may be a Pontobdella.

[467]

Ann. Mag. Nat. Hist. (6) xii. 1893, p. 75.

[468]

Memorie sulla Storia e Notomia degli Animali senza Vertebre, 1823.

[469]

Histoire Naturelle des Animaux sans Vertèbres, vol. iii. 1816, p. 76.

[470]

Le Règne Animal, 2nd ed. 1830.

[471]

γέφῦρα = a bridge, Ann. Sci. Nat. (3), vol. vii. 1847, p. 340.

[472]

Fischer, Abh. Ver. Hamburg, Bd. xiii. 1895, p. 1.

[473]

Cuénot, Arch. Zool. exp. (2) ix. 1891, p. 593.

[474]

Bull. Mus. Harvard, vol. xxi. 1891, p. 143.

[475]

Shipley, Quart. J. Micr. Sci. vol. xxxi. 1890, p. 1.

[476]

Stud. Johns Hopkins Univ. vol. iv. 1887-90, p. 389.

[477]

Conn, Stud. Johns Hopkins Univ. vol. iii. 1884-87, p. 351.

[478]

Arb. Instit. Wien, Bd. v. 1884, p. 61.

[479]

Shipley, Quart. J. Micr. Sci. vol. xxxii. 1891, p. 111.

[480]

Proc. Roy. Soc. Edin. xviii. 1892, p. 17.

[481]

Selenka, Die Sipunculiden. Semper's Reisen im Archipel d. Philippinen, vol. iv. 1883.

[482]

Stud. Johns Hopkins Univ. vol. iv. 1887-90, p. 389.

[483]

Selenka, Challenger Reports, vol. xiii. 1885.

[484]

Ann. Sci. nat. (7) vol. xx. 1895, p. 1.

[485]

Zool. Anz. ix. 1886, p. 574.

[486]

This is not true of all species.

[487]

Acta Ac. German, Halle, xli. Part II. No. 1, 1879.

[488]

Recueil Zool. Suisse, iii. 1886, p. 313.

[489]

Vide p. [335].

[490]

P. Phys. Soc. Edinb. vol. i. 1856, p. 165; and Edinb. New Phil. Journ. vol. iv. (n.s.) 1856, p. 313; Ann. Sci. Nat. 4th ser. vol. xi. 1859, p. 150; and F. D. Dyster, Tr. Linn. Soc. London, vol. xxii. 1859, p. 251.

[491]

Ann. Sci. Nat. 4th ser. vol. x. 1858, p. 11.

[492]

"Beiträge zur Anatomie der Phoronis," Inaug. Dissert. Prag. 1889, and Zeitschr. wiss. Zool. vol. li. 1891, p. 480.

[493]

P. Linn. Soc. N. S. Wales, 1st ser. vol. vii. 1883, p. 606; and 2nd ser. vol. vii. 1893, p. 340.

[494]

Quart. J. Micr. Sci. vol. xxx. 1890, p. 125.

[495]

Challenger Reports, vol. xxvii. 1888; and Proc. Roy. Soc. Edinb. vol. xi. 1882, p. 211.

[496]

Proc. Roy. Soc. London, vol. xxxiv. 1883, p. 371.

[497]

Zapiski Acad. St. Petersb. vol. xi. No. 1, 1867 (Russian). Abstract in Arch. Naturg. Jahrg. xxxiii. 1867, Bd. ii. p. 235.

[498]

Caldwell, loc. cit. Foettinger, Arch. Biol. vol. iii. 1882, p. 679; Gegenbaur, Zeitschr. wiss. Zool. vol. v. 1854, p. 345; Krohn, Arch. Anat. Jahrgang 1858, p. 289; Metschnikoff, Nachricht. k. Ges. Wiss. Göttingen, No. 12, 1869, p. 227, and Zeitschr. wiss. Zool. vol. xxi. 1871, p. 233; J. Müller, Arch. Anat. Jahrgang 1846, p. 101; Schneider, Monatsber. Ak. wiss. Berlin, 1861, p. 934, and Arch. Anat. Jahrgang 1862, p. 47; Wagener, Arch. Anat. Jahrgang 1847, p. 202; Wilson, Amer. Natural. vol. xiv. 1880.

[499]

Proc. Roy. Soc. Edinb. vol. xxi. 1896, p. 59; and Zool. Anz. xix. 1896, p. 266.

[500]

The account given in the following pages has been deliberately restricted, for the most part, to British species. Our own fauna contains an assemblage of Polyzoa which is so representative that it has seemed better to do some justice to the British forms than to attempt to cover the whole ground in the limited number of pages devoted to this group. Those who desire to make a wider study of the subject should refer, for marine forms, to Busk's Catalogue of Marine Polyzoa in the Collection of the British Museum, Parts I.-III. 1852, 1854, 1875; to the Challenger Reports on Polyzoa, Parts 30 (1884), 50 (1886), and 79 (1888); for references and lists of species, to Vine's Report on Recent Marine Polyzoa, Cheilostomata and Cyclostomata (Report, 55th meeting Brit. Ass. Aberdeen, 1885, pp. 481-680); [and to Nickles and Bassler, Synopsis Amer. Foss. Bryozoa incl. Bibliography (Bull. U.S. Geol. Survey, No. 173, 1900)]. References to the literature of the fresh-water forms will be found below, in Chap. XVIII.

[501]

Hooker, quoted by Landsborough, Hist. Brit. Zoophytes, 1852, p. 346.

[502]

Rare and Remarkable Animals of Scotland, ii. 1848, p. 15.

[503]

Arch. Zool. Exp. 2 sér. x. 1892.

[504]

Kraepelin, Abh. Ver. Hamburg, x. 1887, No. ix. p. 19; κάμπτειν, to bend; δέρμα, skin.

[505]

Parts of the ectocyst of some calcareous forms are covered by an external investment of cells, which give rise to secondary thickenings, ridges, and other growths.

[506]

From the Quart. J. Micr. Sci. xxxiii. 1892.

[507]

Ibid. p. 123.

[508]

Quart. J. Micr. Sci. xxxiii. 1892, p. 147. The experiment was conducted in a laboratory, and the results may not be perfectly normal with regard to the time occupied.

[509]

See also Joliet, Arch. Zool. Exp. vi. 1877, p. 202, and explanation of plate viii. for another series of observations.

[510]

See especially G. J. Allman, Monograph of the Fresh-water Polyzoa, Ray Society, 1856, p. 41; and H. Nitsche, Zeitschr. wiss. Zool. xxi. 1871, p. 479.

[511]

Ray Society, 4to, 1856.

[512]

Zoological Researches and Illustrations, v. "On Polyzoa." Cork, 1830.

[513]

"Symbolae Physicae," 1831, and Abh. Ak. Berlin, 1832, i. p. 377, etc.

[514]

T. cit. p. 92.

[515]

Vol. i. 1880, Introduction, p. cxxxi.

[516]

Élémens de Zoologie, 2nd ed. Animaux sans Vertèbres, 1843, pp. 238, 312. Prof. A. Milne-Edwards has kindly written to me, informing me that he believes this to have been the first occasion on which the term was thus used.

[517]

Phil. Trans. vol. cxliii, 1853, p. 62.

[518]

Nitsche, Zeitschr. wiss. Zool. xx. 1870, p. 34.

[519]

πρωκτός, anus; ἐντός, within; ἐκτός, without.

[520]

λοφός, crest or tuft.

[521]

γυμνός, naked; λαιμός, throat.

[522]

φυλάσσω, I guard.

[523]

κύκλος, circle; στόμα, mouth.

[524]

χεῖλος, lip.

[525]

κτείς, κτενός, comb.

[526]

Miss E. C. Jelly, Synonymic Cat. Recent Marine Bryozoa, London, 1889.

[527]

Zeitschr. wiss. Zool. xxi. 1871, p. 421.

[528]

Fischer, Nouv. Arch. Mus. Paris, ii. 1866, p. 293.

[529]

Ehlers, Abh. Ges. Göttingen, xxi. 1876, p. 3, and Joyeux-Laffuie, (as Delagia) Arch. Zool. Exp. 2 sér. vi. 1888, p. 135.

[530]

Busk, "Challenger" Reports, Parts 30 and 50.

[531]

Hincks, Brit. Marine Polyzoa, Introduction, p. cxxxv.

[532]

Hincks, Brit. Mar. Polyzoa, i. p. 558.

[533]

See Hincks, Brit. Mar. Polyzoa, i. p. lxiv.; and Busk, Cat. of Marine Polyzoa in the British Museum, part ii. 1854, p. 103.

[534]

J. Linn. Soc. xv. 1881, p. 359.

[535]

"Challenger" Report, part xxx. 1884, pl. ix.

[536]

Hincks, Brit. Mar. Polyzoa, i. p. 58.

[537]

Brit. Mus. Cat. part ii. 1854, p. 106; Hincks, t. cit. p. 181 n.

[538]

p. [475].

[539]

Barentsia Hincks (= Ascopodaria Busk) differs from Pedicellina in that each stem has a muscular swelling at its base. The genus is represented by two British species, B. gracilis Sars and B. nodosa Lomas.

[540]

Arch. Zool. Exp. 2 sér. ix. 1891, p. 91.

[541]

For structure, see Davenport, Bull. Mus. Harvard, xxiv. 1893, p. 1.

[542]

λοξός, oblique; σῶμα, body.

[543]

Quart. J. Micr. Sci. xxvii. 1887, pl. xxi. Fig. 10.

[544]

For a recent account of the Entoprocta, see Ehlers, "Zur Kenntniss d. Pedicellineen," Abh. Ges. Göttingen, xxxvi. 1890, No. iii.

[An important account of the structure of marine Ectoprocta is given by Calvet, "Contribution à l'Histoire Naturelle des Bryozoaires Ectoproctes Marins," Trav. Inst. Zool. Montpellier, N.S., Mém. No. 8, 1900.]

[545]

Kraepelin, K., "Die deutschen Süsswasser-Bryozoen."—Abh. Ver. Hamburg, x. 1887, No. 9, p. 95.

[546]

Jullien, Bull. Soc. Zool. France, x. 1885, p. 92.

[547]

Hincks, Brit. Marine Polyzoa, i. p. 132.

[548]

T. cit., p. 167.

[549]

Quoted by Kraepelin, t. cit., p. 83.

[550]

Kraepelin, Abh. Ver. Hamburg, xii. 1893, No. 2, p. 65.

[551]

Zool. Anz., xvi. 1893 (1894), p. 385.

[552]

Hyatt, Proc. Essex Institute (U.S.A.) (reprint from vols. iv., v. 1866-1868), p. 9.

[553]

Rare and Remarkable Animals of Scotland, ii. 1848, p. 93.

[554]

Trembley, Mém. Hist. Polypes, 1744; iii. Mém., p. 217. The same processes are described by Baker, Employment for the Microscope, new ed. 1785, p. 311.

[555]

Oka, J. Coll. Japan, iv. 1891, p. 90.

[556]

Hyatt, t. cit. p. 99.

[557]

Verworn, Zeitschr. wiss. Zool. xlvi. 1888, p. 119.

[558]

Dalyell, t. cit. p. 94.

[559]

Kraepelin, Abh. Ver. Hamburg, x. 1887, No. 9, p. 141.

[560]

Phil. Trans. 1837, p. 396.

[561]

Zeitschr. wiss. Zool. xxi. 1871, p. 426.

[562]

J. Coll. Japan, iv. 1891, p. 113.

[563]

Zool. Anz. xii. 1889, p. 508. This paper contains references to M. Jullien's writings on the mechanism of protrusion.

[564]

[See P. Cambridge Soc. vol. xi. Part 1, 1901.]

[565]

Zeitschr. wiss. Zool. xlvi. 1888, p. 124.

[566]

Kraepelin, Abh. Ver. Hamburg, xii. 1893, No. 2, p. 47; Braem, Bibl. Zool. (Bd. ii.) Heft 6, 1890, pp. 66 f.

[567]

Cf. Kraepelin, Abh. Ver. Hamburg, x. 1887, No. 9, pp. 154 f.

[568]

T. cit. p. 83.

[569]

Joliet, Arch. Zool. Exp. vi. 1877, p. 262.

[570]

Kraepelin, Abh. Ver. Hamburg, xii. 1893, No. 2, p. 22.

[571]

Harmer, Quart. J. Micr. Sci. xxxiv. 1893, p. 211.

[572]

Arch. Zool. Exp. 2 sér. x. 1892, p. 557.

[573]

Phil. Trans. 1837, p. 408.

[574]

Brit. Marine Polyzoa, Introduction, pp. lxxxvi, xc.

[575]

Arch. Zool. Exp. vi. 1877, p. 261.

[576]

Recherches sur l'Embryologie des Bryozoaires, 4to Lille, 1877.

[577]

Prouho, loc. cit.

[578]

Arch. Zool. Exp. 2 ser. v. 1887, p. 446.

[579]

Quart. J. Micr. Sci. xxxiv. 1893, p. 199; xxxix. part i. 1896, p. 71.

[580]

Jullien, Mém. Soc. Zool. France, iii. 1890, p. 381.

[581]

Cori, Zeitschr. wiss. Zool. lv. 1893, p. 626.

[582]

Oka, J. Coll. Japan, iv. 1891, p. 109; viii. 1895, p. 339.

[583]

Cf. Seeliger, Zeitschr. wiss. Zool. xlix. 1890, p. 168; and l. 1890, p. 560.

[584]

Cf. Milne-Edwards (H.), Ann. Sci. Nat. 2 ser. vi. 1836, pp. 5, 321.

[585]

See Norman, Ann. Nat. Hist. ser. 6, xiii. 1894, p. 114.

[586]

See Holdsworth, P. Zool. Soc. pt. xxvi. 1858, p. 306.

[587]

Brit. Mar. Polyzoa, Introduction, p. cxxii.

[588]

Ann. Nat. Hist. ser. 5, xx. 1887, p. 91.

[589]

Aetea, Eucratea, and certain other forms were separated off by Mr. Busk as a distinct division, the Stolonata.

[590]

Most of the writings of this author are referred to on pp. 277, 278 of Miss Jelly's Synonymic Catalogue, referred to on p. [523].

[591]

Catalogue of Marine Polyzoa in the Collection of the British Museum, parts i.-iii. 1852-1875; and Challenger Reports, Parts 30 (1884) and 50 (1886).

[592]

Trans. and Proc. R. Soc. Victoria, xxiii. 1887, p. 187, and Tr. R. Soc. Victoria, iv. 1895, p. 1.

[593]

Tr. Zool. Soc. xiii. 1895, p. 223.

[594]

Zittel, Text Book of Palaeontology (Eng. Trans.), 1900, p. 257 (Bryozoa, by E. O. Ulrich).

[595]

Paléontologie Française. Terrains Crétacés, tome v., Bryozoaires, 8vo. Paris, 1850-1851. This great work refers, however, to recent as well as to fossil species.

[596]

Heteropora, of which recent species exist, is placed by Dr. Gregory in the Trepostomata.

[597]

Quart. J. Geol. Soc. l. 1894, pp. 72, 79.

[598]

See, however, Vine, Ann. Nat. Hist. ser. 5. xiv. 1884, pp. 87, 88, and P. Yorksh. Geol. Soc. xii. 1891, p. 74, for possible Palaeozoic Ctenostomes (Ascodictyon, Rhopalonaria, and Vinella).

[599]

Two vols. 8vo. London (Van Voorst), 1880.

[600]

8vo. London (Dulau), 1889.

[601]

One or two genera of Cheilostomata may be mistaken for Cyclostomata. In case of doubt, 7 et seq. must be worked through.

[602]

Certain varieties of adherent species occasionally assume an erect form.

[603]

For Celleporella (colony minute: orifice tubular), see 41 et seq.

[604]

Rhynchozoon (see No. 61), in which the primary orifice becomes much obscured by the development of a large mucro, is placed in this section.

[605]

Hincks, J. Linn. Soc. xxi. 1889, p. 123.

[606]

Micropora complanata, Norman, should be placed in the genus Lepralia. See Hincks, Ann. Nat. Hist. 5 ser. xix. 1887, p. 304.

[607]

See Norman, Ann. Nat. Hist. ser. 6, xiii. 1894, p. 113.

[608]

Hincks, "Marine Polyzoa" (reprints from Ann. Nat. Hist. 1880-91), Index, p. v. note. (Replacing Rhynchopora, preoccupied for a Brachiopod.)

[609]

A form of Lepralia pallasiana, in which a mucro is developed, may be mistaken for Umbonula (see characters given for Lepralia under No. 59).

[610]

See Arch. Zool. Exp. 2 ser. vi. 1888, p. 135 (as Delagia), and ibid. x. 1892, p. 594. [See also J. Mar. Biol. Ass. v., 1897-99, p. 51.]

[611]

F. S. Conant, Johns Hopkins Univ. Circ. vol. xv. 1896, p. 82.

[612]

Ibid. vol. xiv. 1896, p. 77.