102 BENSLEY. [VOL. II. 



The second problem is less simple. Because of the very 

 exceptional conditions introduced in the case of the frog by 

 the herbivorous diet of the tadpole, and of the very extensive 

 histolytic changes which take place in the whole intestine dur- 

 ing metamorphosis, it becomes difficult to discuss this question 

 from the standpoint of histogenesis. The question is, whether 

 the oesophageal glands of the frog, like those of Proteus and 

 Necturus, are to be regarded as somewhat modified anterior 

 gastric glands. Let us examine, in the first place, the ana- 

 tomical characters on which the subdivision of the foregut has 

 been determined in this form. According to Wiedersheim (12) 

 the stomach begins at a point where the foregut experiences 

 an abrupt turn to the left. This is found on examination to 

 correspond to the point where the ciliated epithelium is suc- 

 ceeded by the cylindrical epithelium of the stomach. There 

 is also a slight constriction at this point and a change in the 

 color of the mucous membrane. Of these the only character 

 of importance is the change of epithelium. This is not, in my 

 opinion, a valid criterion for the following reasons : In Amblys- 

 toma ciliated epithelium is found in the anterior portion of 

 the stomach up to a late stage of development. In the tad- 

 pole, according to Gage, the whole foregut is ciliated, and 

 several observers record patches of ciliated cells in the stomach 

 of the adult frog. In several of our American "ganoids," 

 Hopkins (4) and Macallum (9) describe the ciliated epithelium 

 as being continued over a considerable portion of the stomach. 



It is true that the differences in the cells of the oesophageal 

 and gastric glands of the frog are very striking ; but if we 

 compare the oesophageal glands of the frog with the gastric 

 glands of any Urodele or of Bufo, these differences are not 

 apparent. The same cellular elements are present, with almost 

 the same arrangement and structure. 



The gastric glands of the frog are, in fact, unique among 

 the Batrachia, in the small amount of zymogen which they 

 contain. May this not be but another instance in which this 

 animal, as compared with other Batrachia, exhibits an unusual 

 degree of specialization, the anterior gastric glands (so-called 

 oesophageal glands) having retained and developed the zymogenic 



