430 HOPKINS. [Vol. XI. 



Amia. 



In this, the most teleostoid in appearance of Ganoids, one 

 might, perhaps, expect to find morphological features unlike 

 those of the other members of the group. Macroscopically, 

 the enteron of Amia does differ to a certain extent from the 

 others, but microscopically the resemblances are very close. 

 But little, if any, taxonomic value can be ascribed to this organ 

 so far as could be ascertained from the individuals examined. 

 The general form of the enteron in Amia is shown in Fig. 4. 

 The chief differences between this and the preceding are that 

 in Amia the gastric portion of the enteron is, comparatively, 

 very much enlarged and of somewhat different shape, and there 

 are no pyloric caeca. The spiral valve makes four or four and 

 one-half turns, the last ending a little more than a centimeter 

 from the vent. 



In the adult specimens examined there was no distinct ven- 

 tral mesentery connecting this part of the intestine with the 

 ventral abdominal wall as in Lepidosteus. Papillae were not 

 found back of the pharyngeal dental pads. The fibers of the 

 circular muscular coat are striated as far as to the place where 

 the glands of the stomach first appear, just caudad of the pneu- 

 matic duct opening; elsewhere unstriated fibers were found. 

 The pneumatic duct opens near the junction of the oesophagus 

 and stomach. Between oesophagus and stomach is a short 

 region occupied by rather short, broad follicles lined by colum- 

 nar ciliated cells; the true gland cells are first seen at a point 

 a little beyond the opening of the pneumatic duct. 



According to Schulze (58) the epithelial cells of the stomach 

 in all vertebrates are open, i.e., the free ends of the cells are 

 not covered by a cell wall. 



The mucus which these open cells secrete, Edinger thinks, 

 is for the purpose of protecting the cells themselves from the 

 digestive action of the secreted fluids. Brinton (i i) also seems 

 to hold the same opinion. He says: "The protection of the 

 stomach from its own secretion is effected mainly by the sali- 

 vary and other secretions which enter it from the oesophagus 

 and the duodenum. . , . For units of mucous membrane. 



