THE STOMACH. 337 



already considered, and which, in the Ascidia and in the 

 Amphioxus, traverses the middle of the gill-body, and is of 

 great importance in conducting the food into the stomach 

 (vol. i. p. 420; Plate XL Figs. 14-16, 2/)- 189 



The second main section of the intestinal canal, the 

 stomach or digestive intestine, undergoes modifications no 

 less important than those affecting the first main section. 

 On tracing the further development of this digestive section 

 of the intestinal tube, we again find a very complex and 

 composite organ eventually produced from a very simple 

 rudiment. For the sake of rendering the matter more 

 intelligible, we may distinguish the digestive intestine 

 into three parts : the fore intestine (with the gullet and 

 stomach) ; the middle intestine, the gall-intestine (with the 

 liver and pancreas) ; the empty intestine (jejunum}, and 

 crooked intestine (ileus); and the hind intestine (large 

 intestine and rectum). Here we again find protuberances 

 or appendages of the originally simple intestinal tube 

 which change into very various structures. We have 

 already discussed two of these appendages the yelk-sac, 

 which protrudes from the middle of the intestinal tube 

 (Fig. 286, c), and the ailantois, which grows out of the 

 last portion of the pelvic intestine as a large sac-like 

 protuberance (w). The protuberances from the middle 

 of the intestine are the two great glands which open 

 into the duodenum, the liver (h) and the ventral salivary 

 gland. 



Immediately behind the bladder-like rudiment of the 



lungs (Fig. 286, 1) comes that portion of the intestinal tube 



which forms the most important part of the digestive 



apparatus, viz., the stomach (Figs. 284, d, 285, 6). This sac- 



VOL. n. z 



