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 



Oe 



IHD 



FIG. 188. INTESTINAL TRACT OF PERCH. 



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

 Ap, pyloric caeca (appendices pylorieae) ; 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, -K). 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 ossophagus 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 oesophagus of marine Chelonians, like that of many Birds, is lined by 

 horny papillae. 



