The highly developed and complicated structure of the caecal apparatus in _Iguana_ and allied forms exemplifies very clearly the influence of _vegetable_ food on the development of this segment of the alimentary tract when compared with the simple type of ileo-colic transition found in _carnivorous_ lizards, as _Heloderma_ (Fig. 322). _Iguana_ subsists on leaves, fruits and other vegetable matter and the caecal pouch is invariably found filled with the firmer and less digestible portions of this food. These are undoubtedly retained in the pouch by the series of valves and folds until digestion and absorption of all available nutritive material forwarded from the small intestine is completed. On the other hand _Heloderma_ lives almost entirely on bird eggs, a concentrated and easily digested food. Consequently the ileo-colic junction in this lizard is exceedingly simple and rudimentary, marked merely by a slight external constriction, with an annular valve in the interior, and an increase in the caliber of the short hindgut, resembling the form found in many teleost fishes. 4. Finally in some Ophidians a typical lateral caecal pouch of considerable dimensions is found connected with the endgut immediately beyond the ileo-colic junction. An example of this reptilian type, closely resembling the corresponding structure in many Mammalia, is presented by _Eunectes marinus_, the anaconda, shown in Figs. 331 and 332. [Illustration: FIG. 331.--_Eunectes marinus_, anaconda. Mid- and end-gut, with ileo-colic junction and caecum. (Columbia University Museum, No. 72/1535.)] [Illustration: FIG. 332.--_Eunectes marinus_, anaconda. Mid- and end-gut, with ileo-colic junction and caecum laid open. (Columbia University Museum, No. 1709.)] IV. ILEO-COLIC JUNCTION IN BIRDS. In the birds the length of the intestine is subject to great variations. The canal is short in species subsisting on fruits and insects, long in those feeding on seeds, plants and fish. The large intestine, immediately beyond the ileo-colic junction, is provided typically with two symmetrical lateral caeca which extend in some forms for a considerable distance cephalad on each side of the small intestine to which they are bound by peritoneal connections. [Illustration: FIG. 333.--_Buteo harloni_, black hawk. Ileo-colic junction and caeca. (Columbia University Museum, No. 1502.)] [Illustration: FIG. 334.--_Phalacrocorax dilophus_, double-crested cormorant. Ileo-colic junction and caeca. (Columbia University Museum, No. 67/1534.)] [Illustration: FIG. 335.--_Gallus bankiva_, hen. Ileo-colic junction and caeca. (Columbia University Museum, No. 1486.)] [Illustration: FIG. 336.--_Chen hyperborea_, Canada snow-goose, Ileo-colic junction and caeca. (Columbia University Museum, No. 47/1448.)]