[Illustration: FIG. 314.--_Gadus callarias_, cod-fish. Ileo-colic junction. Intestine on each side opened, with probe passed through constricted opening of ileo-colic valve. (Columbia University Museum, No. 1260.)] [Illustration: FIG. 315.--_Pleuronectes maculatus_, flounder. Ileo-colon, opened to show ileo-colic valve. (Columbia University Museum, No. 1493.)] [Illustration: FIG. 316.--_Galeus canis_, dog-shark, male. Genito-urinary tract and cloaca _in situ_. (Columbia University Museum, No. 1694.)] [Illustration: FIG. 317.--_Accipenser sturio_, sturgeon. Alimentary canal. (Columbia University Museum, Nos. 1826, 1827, and 1828.)] II. AMPHIBIA. The alimentary canal is simple and usually comparatively short. There is no caecal pouch. Differentiation of mid- and endgut is usually marked externally by a constriction and by the increased caliber of the terminal intestinal segment. [Illustration: FIG. 318.--_Rana catesbiana_, bull-frog. Alimentary canal and appendages. (Columbia University Museum, No. 1454.)] [Illustration: FIG. 319.--_Necturus maculatus_, mud-puppy. Alimentary canal and appendages. (Columbia University Museum, No. 1582.)] [Illustration: FIG. 320.--_Cryptobranchus alleghaniensis_, hellbender. Ileo-colic junction. (Columbia University Museum, No. 1711.)] Fig. 318 shows the alimentary canal of the bull-frog, _Rana catesbiana_, Fig. 319 that of a Urodele Amphibian, _Necturus maculatus_, and Fig. 320 the ileo-colic junction isolated in _Cryptobranchus alleghaniensis_, the hellbender. III. REPTILIA. In reptiles a well-marked differentiation of small and large intestine is the rule. Four types of ileo-colic junction are encountered in this class: 1. The transition from small to large intestine is marked by the greatly increased caliber of the latter and by an annular valve in the interior. An example of this type is furnished by _Alligator mississippiensis_ (Fig. 321) and a similar form is encountered in some lizards, as _Heloderma suspectum_, the Gila monster (Fig. 322). [Illustration: FIG. 321.--_Alligator mississippiensis_, alligator. Ileo-colon; dried preparation. (Columbia University Museum, No. 179.)] [Illustration: FIG. 322.--_Heloderma suspectum_, Gila monster. (Columbia University Museum, No. 69/1536.)] 2. The large intestine immediately beyond the ileo-colic junction protrudes along the convex border to form a rudimentary lateral caecum. This type is found in many Chelonians, _e. g._, in _Pseudemys elegans_, the pond turtle (Figs. 323 and 324) and _Chelydra serpentaria_, the snapping turtle (Fig. 325). [Illustration: FIG. 323.--_Pseudemys elegans_, pond-turtle. (Columbia University Museum, No. 1069.)] [Illustration: FIG. 324.--_Pseudemys elegans_, pond-turtle. Ileo-colic junction, opened. (Columbia University Museum, No. 1524.)] [Illustration: FIG. 325.--_Chelydra serpentaria_, snapping turtle. Intestinal canal, pancreas, and spleen. (Columbia University Museum, No. 1369.)]