SOPHAGUS, STOMACH, AND INTESTINE. 



231 



With the exception of the Cyclostomi, Holocephali, Ganoidei,and 

 Teleostei, in which there is a separate anus, the large intestine of 

 all other Fishes, and of Dipnoi and Amphibia, opens into a cloaca, 

 common to it and to the urinogenital ducts. The large intestine 

 takes a straight course, and in Amphibia, as well as to some extent 

 in certain Ganoids and Teleosteans, is plainly marked off from 



FIG. 188. INTESTINAL TRACT OF PERCH. 



Oe, oesophagus ; M, stomach; t, caecal process of latter ; P, P, short pyloric region ; 

 -dp> pyloric caeca (appendices pyloricae) ; MD, small intestine ; ED, rectum ; 

 A, anus. 



the small intestine : in some cases it is considerably swollen, 

 even exceeding the stomach in capacity (Fig. 190, N). An out- 

 growth of the ventral wall of the cloaca in Amphibia gives 

 rise to the urinary bladder, and represents the rudiment of 

 the allantois. 



Reptiles. Corresponding with the more definitely differen- 

 tiated neck, we find that Reptiles have a longer oesophagus than 

 the animals as yet considered, and this is always plainly marked 

 off from the much wider stomach, which is usually sac-like, or 

 bent upon itself, when it lies transversely (Chelonians). 1 The 

 stomach of Crocodiles is more specialised than that of other 

 Reptiles, and approaches that of Birds in structure. 



Snakes, Snake-like Lizards, and Amphisbaenians pos- 

 sess a narrow, spindle-shaped stomach which lies in the long axis 

 of the body ; in correspondence with the large size of the masses of 



1 The O3sophagus of marine Chelonians, like that of many Birds, is lined by 

 horny papillae. 



