64 



portion of the post-pyloric intestine which bears the 

 pyloric ciBca and receives the bile and pancreatic ducts. 

 There is no essential difference between intestine and 

 rectum, but it is convenient to distinguish the terminal 

 portion of the alimentary canal from that immediately 

 preceding it. 



The appearance presented by the viscera on opening 

 the body cavity of a large plaice from the ocular side 

 varies considerably with the condition of the reproductive 

 organs and with the sex. Fig. 20, pi. V., represents the 

 relations of the viscera in a " ripe " and mature female. 

 The great increase in volume of the ovaries has crowded 

 the greater portion of the intestine towards the dorsal 

 part of the body cavity ; the duodenum is pressed for- 

 ward ; the rectum being more fixed than the rest of the 

 post-pyloric intestine is not much displaced : the stomach 

 occupies nearly its normal position. Fig. 21 shows the 

 condition of the viscera in a mature female which has just 

 spawned. The greater portion of the intestine has been 

 removed, however, in order to display the deeper viscera. 

 It would form two S-shaped loops overlying and hiding 

 most of the structures indicated in the figure. 



The (Esophagus is very short, and almost immediately 

 on entering the bodv cavity expands into the ttomach. 

 Its walls are very thick and are composed almost entirely 

 of a transversely disposed layer of striated muscle fibres. 

 The external longitudinal muscle layer is thin, and 

 appears to consist of unstriated fibres. The mucosa con- 

 sists of a layer of columnar cells crowded with " goblet " 

 cells. As observed in the dead fish, the lumen of the 

 oesophagus is greatly reduced, though it is evident from 

 the nature of the food that it is capable of considerable 

 expansion. 



The layer known as the muscularis mucosae does not 



