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. [Illustration: 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. [Sidenote: 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. [Sidenote: Bay VIII.] [Sidenote: Bay IX.]