The Central Hall.
Statues and Cases in the Central Hall.
On entering the hall the visitor will notice the bronze statue of the late Sir Richard Owen, K.C.B., Superintendent of the Natural History Departments of the British Museum (1856–1884). It is the work of Mr. T. Brock, R.A., and was placed in the Museum on March 17th, 1897. To the right of this is a marble statue of the late Professor T. H. Huxley, sculptured by Mr. E. Onslow Ford, R.A., which was unveiled on April 28th, 1900. In the first bay on the left is a bust, by Mr. Brock, of the late Sir W. H. Flower, Director of the Natural History Departments of the British Museum from 1884 to 1898. Most of the cases placed on the floor of the hall illustrate general laws or points of interest in natural history which do not come appropriately for illustration within the systematic collections of the departmental series.
Pigeons illustrating Variation under Domestication.
One group, in a case near the entrance to the hall, on the right, shows the great variation to which a species may become subject under the influence of domestication, as illustrated by examples of the best-marked breeds of Pigeons, all derived by selection from the wild Rock-Dove (Columba livia), specimens of which are shown at the top of the case.
Fowls and Canaries illustrating Variation under Domestication.
In the corresponding case on the left are further illustrations of the same subject. A pair of red Jungle Fowl (Gallus bankiva, or G. ferrugineus) of India represents the species from which the breeds of Domesticated Fowls are generally considered to have been derived. As examples of extreme modifications in opposite directions produced by selection, are exhibited the Japanese Long-tailed Fowls, in which some of the feathers (tail-coverts) attain a length of nine feet, and specimens of a breed in which the tail is absent. There is also shown a group of Fowls living wild in the woods of the Fiji Islands, which are descendants from domesticated birds introduced in the eighteenth century. A pair of Cochin Fowls is exhibited in the same case to display development in point of size and in the abundance of feathers on the limbs; while a pair of white “Silkies” illustrates a modification of the plumage, accompanied by a rudimentary condition of the tail-feathers. The pair of Coloured Dorkings exemplifies a breed cultivated in England.
A series of Canaries is shown in a case in the archway leading from the east side of the central hall to the north hall, as an example of a late addition to domesticated animals, these birds having been first imported into Europe from the Canary Islands in the early part of the sixteenth century. Specimens are exhibited of the wild birds, and of some of the modifications produced by selection.
Ruffs and Reeves, illustrating Changes of Plumage according to Sex and Season.
A case placed to the north of the one containing Fowls illustrates a remarkable instance of external differences in the two sexes and changes in plumage at different seasons, not under the influence of domestication. The birds in it belong to one species, the Ruff (Pavoncella, or Machetes, pugnax), of which the female is called Reeve; a member of the Plover family (Charadriidæ). In the upper division of the case are shown the eggs, newly-hatched young, and young males and females in the first autumn plumage; as well as adult males and females in winter, when both sexes are exactly alike in colour and distinguishable externally by size alone. The large group occupying the lower part of this case consists of adult birds in the plumage assumed in the breeding time (May and June). In the female the only alteration from the winter state is a darker and richer colouring, but in the males there is a special growth of elongated feathers about the head and neck, constituting the “ruff” from which the bird derives its name. In addition to this peculiarity, another, rare among wild animals, may be observed, namely, striking diversity of colour in different individuals. Of the twenty-three specimens shown no two are entirely alike.
Wild Ducks illustrating Seasonal Change of Plumage.
Next in order stands a case displaying the variations, according to season and age, in the plumage of the Wild Duck, or Mallard (Anas boscas). The most noticeable feature in the plumage-changes is the assumption in summer by males of an “eclipse-plumage,” resembling the one worn by females at all seasons. At other times the males are more brilliantly coloured than their partners. The eclipse-plumage corresponds to the winter, or non-breeding, dress of other birds which have a seasonal change.
Adaptation of Colour to surrounding Conditions.
On the same side of the hall follow two cases illustrating the adaptation of the colour of animals to their natural surroundings, by means of which they are rendered less conspicuous to their enemies or their prey. The first contains a specimen of a Mountain or Variable Hare (the common species of the north of Europe), a Stoat, and a Weasel, together with some Willow-Grouse and Ptarmigan, as well as an Arctic Fox, in their summer dresses. All were obtained in Norway, and show the general harmony of their colouring at this season with that of the rocks and plants among which they live. The second case displays examples of the same animals obtained from the same country in winter, when the ground was covered with snow. Such striking changes as these only occur in latitudes and localities where the differences between the general external conditions in the different seasons are extreme, where the snow disappears in summer and remains on the ground during most of the winter. Even some of the species here shown do not habitually turn white in the less severe winters of their southern range, as the Stoat in England and the Variable Hare in Ireland. A few permanent inhabitants of still more northern regions, where the snow remains throughout the year, such as the Polar Bear, Alaskan Bighorn Sheep, Greenland Falcon, and Snowy Owl, retain the white dress throughout the year. The whiteness of these animals must not be confounded with albinism, or whiteness occurring in individuals of species normally of a different colour, which is illustrated in a case on the other side of the hall.
Protective Resemblance of Desert Animals to their Surroundings.
The case on the east side of the hall nearest the great staircase contains examples of conformity of general style of colouring to surrounding conditions, as exemplified by some of the commoner Birds, Mammals, and Reptiles of the Egyptian desert, placed on the stones and sand amid which they habitually dwell. The advantage of this colouring in concealing the herbivorous species from their enemies, and in enabling the carnivorous to approach their prey unperceived, is obvious. Many excellent cases of concealment by adaptation to surroundings, especially in eggs and young Birds, may be seen among the groups in the Bird-gallery.
Mimicry.
More special modifications for the same purpose are shown in the adjacent bay on the east side of the hall by Insects which closely resemble the objects, such as leaves, twigs, etc., among which they dwell. The close imitation of a dead leaf, presented by the Leaf-Butterfly (Callima inachis), when its wings are closed, could not be surpassed. In a further stage of the same condition, called “Mimicry,” the object resembled, or mimicked, is another living animal, belonging to a different species, family, or even order. The resemblance in these instances is also believed to be for protection, or to be in some way advantageous to the animal in which it occurs. We know, however, so little of the habits and life-history of animals in a state of nature that many of the purposes supposed to be served by particular colours or appearances can only be regarded at present as conjectural. Whatever be the real explanation, the facts shown by the specimens in this bay are very curious, and worthy of careful consideration.
Group illustrating Albinism.
The next case on the east side of the middle of the hall contains a series of specimens illustrating albinism, a condition in which the pigment, or colouring matter, usually present in the skin, hair, or feathers, and giving the characteristic hue, is absent. Individuals in this condition occur among many animals of various kinds, and are called “albinos.” In some of the specimens shown in the case the albinism is complete, but in many it is partial, the absence of colouring matter being limited to certain portions of the surface. Other examples of complete or partial albinism are shown in the North Hall.
Fig. 1.—The Leaf-Butterfly (Callima inachis) in Flight and at Rest.
Group illustrating Melanism.
The adjacent case shows examples of the opposite condition called melanism, depending upon an excess of dark colouring matter or pigment in the skin and its appendages, such as hair, feathers, etc., beyond what is commonly met with in the species. This is by no means so frequent as albinism. A black Leopard in the middle of the case is a good illustration. This is not a distinct species, but merely an individual variety of the common Leopard, born from parents of the normal colour. A black Bullfinch is introduced as an example of acquired melanism, this bird having turned black in captivity.
Fig. 2.—The Somali Tsetse-Fly (Glossina longipennis). Enlarged 4 diameters.
Shows the complete closure of the wings in the resting position, and the prominent proboscis, characteristic of the genus.
Group illustrating Intermediate Forms in Nature.
Another group shows that two forms of Crows which appear quite distinct, and, judged by their external characters, might be regarded as different species, may in a state of nature unite, and produce hybrid offspring. In the same case is exhibited a series of Goldfinches to show a complete gradation between birds of different colouring, which have been regarded as different species. Both these examples may by some naturalists be considered instances, not of the crossing of distinct species, but of “dimorphism,” or the occurrence of a single species in nature in two different phases. From whatever point of view they may be regarded, they illustrate the difficulty of defining and limiting the meaning of the term “species,” of such constant use in natural history.
Mosquitoes and Tsetse-Flies.
In the middle line of the hall are placed cases containing greatly enlarged models of certain Insects concerned in the spread of disease, such as Mosquitoes or Gnats ([figs. 3] and [4]), a House-Fly, Tsetse-Fly ([fig. 2]), and Plague-Flea; also still more enlarged gelatine models of mammalian blood-corpuscles, showing the parasites by which they are infested in the diseases respectively communicated by means of Mosquitoes and Tsetses. Models of the parasites themselves are also shown ([figs. 5] and [6]).
Malaria, or ague, is a disease caused by extremely minute parasites which live in the red corpuscles of the blood. Formerly malaria was believed to be contracted by merely breathing the air of marshy districts, but it is now proved that the parasites are transmitted from man to man by the “bite,” or rather “stab,” of a Mosquito or Gnat. The Common Mosquito or Stabbing Gnat (Culex pipiens), [fig. 3], does not transmit the malaria-parasite; the Spot-winged Mosquitoes ([fig. 4]) of the genus Anopheles, abundant in England and nearly all parts of the world, being the carriers. The parasite multiplies not only in the human blood, but in the stomach and tissues of the Gnat—as shown in the models ([fig. 5]).
Tsetse-Flies are African blood-sucking Flies, with the mouth-parts adapted for piercing the skins of wild and domesticated mammals, human beings, and even crocodiles. The blood of some of the larger African animals is sometimes infected with a microscopic parasite ([fig. 6]), which, if sucked up by Tsetse-Flies when feeding, and subsequently introduced by them into the veins of domesticated animals such as horses and cattle, produces the fatal nagana, or Tsetse-Fly disease. Sleeping-sickness in man is caused in a similar manner, and is conveyed from infected to healthy individuals by two kinds of Tsetse-Fly, including that of which an enlarged model, 28 times (linear) natural size, is exhibited. The parasites and the red blood-corpuscles are enlarged 6,000 diameters.
Fig. 3.—(a) The Common Gnat (Culex pipiens). Enlarged.
Fig. 4.—(b) The Spot-winged Mosquito (Anopheles maculipennis). Enlarged.
Fig. 5.—Life-History of the Malaria Parasite.
a, malarial germ, or sporozoite, as introduced into the blood by the mosquito; b, sporozoite after entry into blood-corpuscle; c, growth of sporozoite into an amœbula; d, division of amœbula to form merozoites; e, liberated merozoites; f, growth of merozoites into a crescent at expense of corpuscle; g, male, and h, female crescent; i, male cell with projections, which lengthen and are set free as spermatozoa; j, fertilisation of ovum by spermatozoon; k, fertilised egg as the active motile vermicule; sphere formed from the l, enlarged vermicule, after this has bored through the stomach-wall of the mosquito; m, segment of sphere at final stage of development, containing countless needle-shaped spores, which, when it bursts, escape as sporozoites into the organs of the mosquito’s body and pass through the salivary glands into the proboscis, and so infect a man bitten or pricked by the mosquito.
The House-Fly—see enlarged models of the perfect insect and its preliminary stages,—although not provided with a piercing proboscis, and consequently incapable of biting, sometimes plays an important part in spreading deadly diseases, such as cholera and enteric (typhoid) fever. In this case the disease-causing organisms are carried by the insect either in its intestine or adherent to the outer surface of its body, and thus House-Flies may spread disease by contaminating food.
Plague, which is a disease of rats and a few other rodents, especially the bobac Marmot, is communicated to man by the bite of the flea known as Xenopsylla cheopis, one of several species of fleas with which rats are infested. When a rat dies, the fleas that it has been harbouring seek another host, and may bite human beings, in which case, if the rat itself was suffering from the disease, an epidemic of plague may be the result. The model of the Plague-Flea exhibited is enlarged 200 times (linear).
The Arachnida, a group which includes the Spiders and can generally be distinguished from Insects by the number of their legs (four pairs instead of three pairs), include also the Ticks, which are responsible for the transmission of many deadly diseases which attack Man and Domestic animals. Enlarged models of a disease-carrying Tick are in course of preparation.
Fig. 6.
Trypanosoma gambiense, the parasite of Sleeping-sickness, very highly magnified. The occurrence of three kinds of individual, as shown in the figure, appears to be characteristic of this and certain other species of Trypanosoma.
(After Col. Sir D. Bruce.)
African Elephant.
In the middle line of the hall is placed a magnificent mounted skin of an African Elephant (Elephas africanus), [fig. 7], from Rhodesia, standing about 11 feet 4 inches in height. The skull of the same individual is mounted on a stand below. Near by are exhibited three tusks, the largest of which measures 10 feet 2½ inches in length. On the north wall, on either side of the Darwin statue, are mounted two African Elephant heads.
Bays or Alcoves round the Hall.
Most of the bays or alcoves round the hall, five on each side, are (with the exception of the one at the north end of the right side) devoted to the Introductory or Elementary Collection, designed to illustrate the more important points in the structure of certain types of animal and plant life, and the terms used in describing them. This has been called the “Index Museum,” as it was thought at one time that it would form a sort of epitome or index of the general collections in the galleries. It is now mainly restricted to a display of the leading structural features in Vertebrated Animals and in Plants. The space being limited, the number of specimens is necessarily restricted. In examining this collection the visitor should follow each case in the usual order of reading a book, from left to right, and carefully study the printed explanatory labels, to which the specimens are intended to serve as illustrations.
Fig. 7.—African Elephant (Elephas africanus).
The skull and tusks seen in the foreground are those of the stuffed specimen, the tusks in which have been modelled from another individual.
The bays on the west side (left-hand on entering the hall) are devoted to the Vertebrata, or Animals possessing a “backbone.” In Nos. I and II are shown the characters of the Mammals, which form the highest modification of this type; the wall-cases of No. I containing specimens of the bony framework (internal skeleton).
Bay I. Skeleton of Mammals.
In the first case (south side of the recess) may be seen a complete skeleton of a good example of the class—a Baboon Monkey, with the bones laid out on a tablet, and their names affixed. Below is a skeleton of the same animal articulated, or with the bones in their natural relation to each other, and also named. By examining these two specimens an idea may be obtained of the general framework of the bodies of animals of this class. In other parts of the case are exhibited various modifications of the skeleton to suit different conditions of life.
1. Man, showing a skeleton adapted for the upright posture.
2. A Bat, or flying Mammal, in which, by the great elongation of the fingers, the fore-limbs are converted into wings ([fig. 8]), supporting a web of skin stretched between them.
3. A Sloth, in which the tips of both limbs are reduced to mere hooks, by the aid of which the creature hangs back-downwards from the boughs of the trees among which it passes its entire existence.
4. The Baboon serves as an example of an animal walking on all four limbs in the “plantigrade” position, i.e., with the whole of the palms of the hands and the soles of the feet applied to the ground.
5. A small species of Antelope shows the characteristic form of a running animal, in which the limbs perform no office but that of supporting the body on the ground. This animal stands on the tips of the toes of its elongated, slender feet in the “digitigrade” fashion.
6. A Porpoise, adapted solely for swimming in the water. The fore-limbs are converted into flattened paddles, and the hind-limbs are entirely absent, their function being performed by the tail. The rudimentary pelvic bones are preserved.
The rest of the case is occupied by details of the skull in some of its principal modifications. At the top are diagrams of the structure of bone and cartilage as shown by the microscope.
Fig. 8.—The Skeleton of a Flying-Fox, or Fox-Bat (Pteropus medius).
cl, clavicle; cv, cervical vertebræ; d, dorsal vertebræ; fb, fibula; fm, femur; h, humerus; hx, great toe, or hallux; l, lumbar vertebræ; mc, metacarpals; mt, metatarsals; ph, phalanges, or finger- and toe-bones; pv, pelvis; px, thumb, or pollex; r, radius; s, sacral vertebræ; sc, scapula; sk, skull; tb, tibia; ts, tarsus; u, ulna.
In the wall-case on the opposite (north) side of the bay the study of the skeleton of Mammals is continued by illustrations of the structure of the limbs. At the top of the case is a diagram showing the correspondence of the hand and the foot in their complete typical form, with the names applied to the different bones. The series of specimens below shows the principal deviations actually occurring from this typical condition, which, as may be seen, is very nearly preserved in the human hand. One series shows some of the stages of modification for special purpose (specialisation) by which a typical five-fingered hand becomes converted into the single-toed fore-foot of the Horse; while another series ends with the fore-foot of the Ruminants, sometimes, but erroneously, called a “cloven hoof,” in which only two toes remain. Similar changes are shown in the toes of the hind-foot, illustrating the same common plan running through infinite modifications in detail, enabling the organ to perform such a variety of purposes, and to exhibit such diversity of outward appearance. The existence of this common plan is now generally regarded as due to inheritance from a common ancestor.
Teeth of Mammals.
The central case of the bay contains a collection illustrating the principal characters of the teeth of Mammals. Its inspection should commence at the north-east corner, where the visitor will find himself after completing the survey of the specimens of skeletons in the wall-cases. In the first division are placed specimens showing the general characters of teeth, their form, the different tissues of which they are composed, the two great types of dentition in Mammals, homœodont and heterodont,[5] the names and serial correspondence of the different teeth, and their development and succession. The principal modifications of teeth according to function are next shown by examples of forms adapted for fish-eating, flesh-eating, insect-eating, grass-eating, etc. The remainder of the case is taken up by examples of the dentition of the families of Mammals arranged in order, and prepared so as to display not only the shape of the crowns, but also the number and character of the roots by which they are implanted.
Bay II. Classification of Mammals.
In bay No. II the two wall-cases contain a collection arranged to show in a serial manner the orders and sub-orders of existing Mammals, by examples selected to illustrate the predominating characters by which these are distinguished. A brief popular account of the characteristics of the group, and a map showing its geographical distribution, are placed with each. This is intended to serve not only for an introduction to the study of the class by visitors to the museum, but also as a guide to a method of arrangement which may be adopted in smaller institutions.
Among the illustrations of the order Primates is placed the skeleton of a young Chimpanzee dissected by Dr. Tyson, which formed the subject of his work on the “Anatomy of a Pigmie,” published in 1699, the earliest scientific description of any Man-like Ape.
Skin of Mammals.
The central case of this bay contains illustrations of the outer covering or skin and its modifications in the class of Mammals, divided into the following sections:
1. Expansion of skin to aid in locomotion, as the webs between the fingers of swimming and flying animals, the parachutes of flying animals.
2. The development of bony plates in the skin, found among Mammals only in the Armadillos and their allies. The cast of a section of the tail of a gigantic extinct species (Glyptodon) shows a bony external as well as an internal skeleton.
3. The outer covering modified into true scales, much resembling in structure the nails of the human hand. This occurs in only one family of Mammals, the Pangolins, or Manidæ.
4. Hair in various forms, including bristles and spines. The two kinds of hair composing the external clothing of most Mammals, the long, stiffer outer hair, and the short, soft under-fur, are shown by various examples.
5. The special epidermal appendages found in nearly all Mammals on the ends of the fingers and toes, called according to the various forms they assume, nails, claws, or hoofs.
6. The one or two unpaired horns of the Rhinoceroses, shown by sections to consist of a solid mass of hair-like epidermic fibres.
7. The horns of Oxen, Goats, and Antelopes, each consisting of a hollow conical sheath of horn, covering a permanent projection of the frontal bone (the horn-core).
8. The antlers of Deer, forming solid, bony, and generally branched projections, covered during growth with soft hairy skin, and in most cases shed and renewed annually.
On the wall is arranged a series of antlers of an individual Stag or Red Deer (Cervus elaphus), grown and shed (except the last) in thirteen successive years, showing the changes which took place in their size and form, and the development of the branches, or tines, in each year. In old age the number of these tines tends to diminish.
On the north side of the table-case are shown dissections of the principal internal organs of Mammals.
Bay III. General structure of Birds.
Bay No. III is devoted to the class of Birds. An Albatross (Diomedea exulans) mounted with the wings expanded shows the most important characters by which a Bird is externally distinguished from other animals. The body is clothed with feathers, which (in the majority of Birds), by their great size and special arrangement upon the fore-limbs, enable these to act as organs of flight. The mouth is in the form of a horny beak. A nestling Albatross shows that at this stage of its existence the bird is not clothed with ordinary feathers, but with soft down, which serves to keep the body warm, although it confers no power of flight. An Emu and an Apteryx in the lower compartment of the case display the exceptional condition (found only in a comparatively few members of the class) of Birds with wings so small as to be concealed beneath the general feathery covering of the body, and quite useless. In the Penguins, of which two species are shown in the case, the wings are reduced to the condition of fins, and are serviceable only for progress through water.
In the first wall-case the principal features of the skeleton of the class are shown. Sections of bones exhibit the large air-cavities within; a complete skeleton of an Eagle, with the bones separated and named, and mounted skeletons of the Ostrich, Penguin, Pelican, Vulture, Night-Parrot, Fowl, etc., show the chief modifications of the skeleton. The Apteryx possesses the smallest, and the Frigate-bird the longest bones of the wing, the correspondence of which can be readily traced by means of the labels attached to them. The under surfaces of the skulls of various birds are shown with the different bones coloured to indicate their limits and relations; these are followed by a series of the different types of sternum or breast-bone.
The second wall-case contains further illustrations of the anatomy of Birds. In the left-hand part a series of wings of Birds displays the form characteristic of different groups; while above them are a few of the different types of tails, supplementing the series of tails in the table-case. Very instructive is a series of skins of white chickens of the same brood at different ages, displaying the gradual replacement of the down by the adult plumage.
The table-case in the middle of the bay contains illustrations of the external characters, the beak, the feathers, and the tail, as well as of the fore and hind limbs, or wings and feet. By the aid of the explanatory labels, the essential characters and the principal modifications of all these parts may easily be followed.
Two cases on the wall in the vestibule leading to the Fish Gallery illustrate the chief modifications of the eggs of Birds, and their differences in structure, number, form, size, texture of surface, and colour. On the side of the main staircase opposite are specimens illustrating the parasitic nesting habits of certain Cuckoos and various other Birds; while near by is a remarkably fine series of the eggs of Cuckoos with those of the Birds among which they were respectively deposited. On the opposite (east) side of the staircase the visitor will find a case showing the remarkable variation in colouring and markings displayed by the eggs of the Guillemot.
Bay IV. General structure of Reptiles and Amphibians.
The fourth bay on the west side of the hall exhibits the leading peculiarities in the structure of Reptiles and Amphibians. Owing to the large number of groups in the former class now extinct, many fossil specimens, or plaster reproductions of the same, are shown. The wall-case on the south side of this bay illustrates the different ordinal groups of Reptiles—living and extinct. Very instructive are the skeletons of Tortoises and Turtles, showing the relations of the vertebræ and limb-bones to the bony part of the shell. Lizards and Snakes are mostly represented by coloured casts. The extinct Dinosaurs are represented by a small-sized model of Iguanodon, together with a photograph of the skeleton and a plaster-cast of the bones of the hind-foot showing the three toes.
The adjacent side of the table-case shows the modifications of the backbone, or vertebral column, of the ribs, and of the limbs, in the different groups of the class. Specially noticeable are examples of five types of Skink-like Lizards, exhibiting the gradual diminution in the size of the limbs and their final disappearance.
The opposite, or north, side of the table-case displays the different modifications of the skull and teeth of living and extinct Reptiles. In some, like Crocodiles and Ichthyosaurs, the jaws are armed with a full series of sharply pointed teeth, while in others, like the Tortoises and Turtles, they are devoid of teeth and encased in horn. Very remarkable is the approximation to a carnivorous mammalian type presented by the dentition of some of the extinct mammal-like Reptiles, or Theromorphs, and equally noticeable are the palatal crushing teeth of certain other extinct Reptiles known as Placodus and Cyamodus. The peculiar dentition of the New Zealand Tuatera, and likewise that of its extinct European and Indian ally Hyperodapedon ([fig. 9]), are also shown.
Fig. 9.—Skull of the Giant Tuatera (Hyperodapedon gordoni), from the Triassic Sandstone of Lossiemouth, Elgin, (¼ nat. size). A, upper surface of skull; B, palatal aspect of skull; C, under side of front of lower jaw; Pmx, premaxillary bone; Mx, maxillary; Pl, palatal teeth; Md, lower jaw; O, orbit, or eye-socket; N, nostrils; S, temporal pit; S’, lateral temporal fossa.
The brain and other internal organs of Reptiles are displayed in the left half of the wall-case on the north side of this bay, in which are also shown the eggs of many species, in some cases with the embryo.
Fig. 10.—Skeleton of the Great Blue Shark (Carcharodon rondeletii), with portion of backbone on a large scale. pl, functional upper jaw, and su, its reflected portion; md, lower jaw; hy, ceratohyal; br, branchial arches; co, pectoral girdle; ph, cartilaginous portion of pectoral, or front paired fin; r, dermal portion of pectoral fin; pu, pelvic, or hind paired, fin; c, centra, or bodies, of the vertebræ; na, neural, or upper, and ha, hæmal, or lower, arch. The median fins are not lettered.
In the right half of the same case are exhibited a number of preparations showing the external form and internal structure of Frogs and Salamanders, or Amphibians, living and extinct. The Giant Salamander of Japan (Megalobatrachus or Cryptobranchus) is represented by a stuffed specimen; but the Newts, Salamanders, and Frogs are shown in spirit. Very curious is the almost colourless and blind Olm (Proteus) from the caves of Carniola; as also are the so-called Cœcilians, or Apoda, which have the habits and, in some degree, the appearance of large worms. Special specimens exhibit the structure of the extinct Labyrinthodonts, in which the hinder half of the skull is completely roofed over by bone; while the teeth in many instances exhibit a curious in-folded arrangement from which the group derives its name.
Bay V. Structure of Fishes.
The last bay (No. V) on the west side of the Central Hall is devoted to the display of the form and structure of Fishes.
The wall-case on the left side of this bay exhibits the external form of several characteristic types of Fishes, such as the Pike, Cod, Turbot, Dog-fish, and Skate, with the names of the various fins affixed. A striking specimen is the skeleton—mainly cartilaginous—of the Great Blue Shark (Carcharodon rondeletii), fig. 10, which occupies the greater portion of this case. It should be noted that, as in all Sharks and Rays, the upper jaw does not correspond with that of the higher Vertebrates; and particular attention should be devoted to the structure and arrangement of the arches supporting the gills.
In the south side of the table-case in this bay are shown a number of dissections, mounted in spirit, displaying the different types of skeletal structure presented by the fins in various groups of Fishes. One of the most remarkable of these types occurs in Ceratodus forsteri, the Queensland Lung-fish, in which the skeleton of the fin consists of a central jointed rod, from each side of which diverge narrower jointed rods. Alongside are specimens showing special modifications of certain fins, as in the Flying Fish ([fig. 11]) and Flying Gurnard ([fig. 12]), for the purpose of sustaining the body in the air, or, as in Pentanemus, to serve as organs of touch. Specimens of the West Indian Goby and the Lump-Sucker show modifications of the pelvic fins in connection with a sucker on the lower surface of the body; while other preparations display the pectoral (Doras) and pelvic fins (Monocentris) reduced to the condition of saw-like spines.
The structure of the skull of Fishes is illustrated in another part of the same side of this case. From this the visitor may learn how the primitive cartilaginous skull of the Sharks ([fig. 10]), Rays, Chimæras, and Lung-fishes has been gradually modified, by the addition of superficial sheathing-bones, into the bony skull of modern Fishes, such as the Cod and Perch.
Fig. 11.—The Flying Fish (Exocœtus).
Fig. 12.—The Flying Gurnard (Dactylopterus).
The north side of the table-case in bay V is mainly devoted to the display of the different types of scales, spines, and teeth found among Fishes. In one corner are the enamelled “ganoid” scales of the modern American Bony Pike (Lepidosteus) and the African Bichir (Polypterus) alongside those of certain extinct forms. A scale of the Tarpon, or King-of-the-Herrings, illustrates the largest development in point of size of the modern “cycloid” type. Spines of the Porcupine-fish show an extreme development of this kind of structure. Diagrams and spirit-preparations illustrate the mode of attachment and succession of fish-teeth. A large series of the teeth of Sharks and Rays displays the gradual passage from those of the ordinary pointed form to others arranged in a pavement-like manner and adapted solely for crushing. Both types occur in the Port Jackson Shark ([fig. 13]), but those of some Rays are solely of the pavement modification. Very remarkable is the dental structure in the Parrot-fish. The west end of this side of the case shows the various modifications assumed by the teeth of the modern Bony Fishes; among which, as exemplified by the Wrasse, teeth are developed on the bones of the throat, as well as on those of the jaws. Throughout this case specimens, or models, of the teeth of extinct Fishes are placed side by side with those of their nearest living relatives.
Fig. 13.—A Jaw of the Port Jackson Shark (Cestracion philippi), showing sharp teeth in front and crushing ones behind.
The wall-case on the north side of this bay shows the history of the development of various Fishes, together with the form and structure of the gills, brain, heart, digestive system, and other organs.
Lancelet.
A small case affixed to the pillar at the entrance of the fifth bay illustrates the structure of the Lancelet (Branchiostoma, or Amphioxus), by the aid of spirit-specimens, enlarged models, and coloured diagrams. One of the most remarkable features in the structure of this strange and primitive little creature is the outer cavity enclosing the part of the body which contains the large and complex pharynx. The Lancelet was formerly included among the Fishes, but is now accorded the rank of a class (Cephalochorda) to itself.
Leaving bay VI, next the principal staircase on the east side of the central hall, which is devoted to illustrations of heredity, especially in relation to the Mendelian theory, and to modes of Flight in Vertebrates and Insects, we pass on to a table-case assigned to the illustration of “Mimicry” and kindred phenomena. Most of the examples shown occur among Insects; but one example among Mammals and a second in Birds are illustrated. Very striking is a coloured sketch showing a group of red and black caterpillars from Singapore grouped side by side on the stem of a plant so as to present a remarkable similarity to a succulent fruit.
Bay VIII.
Bay IX.
In bay VIII, on the eastern side of the central hall, is displayed an exhibition illustrating trees, native to or grown in Britain. The winter and summer states are indicated by photographs, and the foliage, flowers, fruits, seedlings, and texture of wood and bark by specimens, models, and drawings. Bays IX and X are intended to illustrate the general characters of the great groups of the Vegetable Kingdom. Bay IX, in course of arrangement, is devoted to the Cryptogams (Ferns, Mosses, Fungi, Seaweeds, and Lichens).
At the back of the bay is a fine polished section of a buttress from the base of the Tapang (Abauria excelsa), the largest tree in Borneo, which attains a height of 250 feet.
Bay X. Seed-bearing Plants.
The last bay (No. X) is devoted to the Seed-bearing Plants, which are characterised by the formation of a seed—the result of the fertilisation of an ovule by the male cell which is developed in the pollen. The series begins on the left hand side with the Pteridosperms, an extinct group combining the characters of Ferns and Seed-plants and forming a link between them. Then follow the Gymnosperms (Cycads, Pines, Firs, etc.), in which the seed is borne naked on an open scale which generally forms, with others like it, the characteristic cone. Certain points in the development of pollen and ovule recall similar stages in the Fern group, and indicate that the Gymnosperms stand nearer to the Cryptogams than do the Angiosperms, the other and larger group of Seed-plants. The Gymnosperms are also the older group, and contain many extinct forms. In the Angiosperms the seed is enclosed in the fruit, and in the development of pollen and ovule almost all traces of a cryptogamic ancestry have been lost; the great development of the flower is a characteristic feature of the Angiosperms. The arrangement of the vegetative parts of the plant is based on its separation into root, stem, and leaf. In the right-hand wall-case the upper series of specimens illustrates the leaf, its form, veining, direction, the characters of its stalk and stipules, its modification for special purposes, and its arrangement on the stem and in the bud. Below, the stem and root are similarly treated, and above are some anatomical drawings. The display of the root is continued in the lower part of the opposite wall-case. In the central case the chief types of the flower with its parts, the fruit, and the seed are exhibited.
At the back of the bay is a large transverse section of the Karri tree (Eucalyptus diversicolor) of Western Australia, a species which grows to a height of 400 feet. The tree from which the section was cut was about 200 years old when felled.
The Introductory Collection of Minerals will be found in the gallery devoted to the Mineral Department (see [p. 90]).