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]).