710 PROCEEDINGS OF THE ACADEMY OF [Dec. , 



cells are present among the bases of the gland and supporting 

 cells, and are demonstrable chiefly by their nuclei. 



The basement membrane of the stomach rests directly upon the 

 inner longitudinal muscle of the body wall. The stomach is fre- 

 quently greatly flattened by the pi*essure exerted by the expanded 

 rhynchocoel. For the study of this region, a specimen from which 

 the proboscis has been cast out is the most favorable. 



The middle intestine, M.I., according to definition, begins with 

 the first pair of lateral intestinal creca, but the cells that are pecu- 

 liarly characteristic of the middle intestine are not found in the 

 most anterior caeca or pouches, which are lined by cells similar to 

 those of the stomach. In other Avoi'ds, the most anterior pouches 

 of the middle intestine belong histologically to the stomach. 



The transition from the gland cells and ciliated supporting cells, 

 exactly similar to those of the stomach, that are found in the 

 most anterior pouches, to the absorptive cells characteristic of the 

 middle intestine is a very gradual one, and varies in different in- 

 dividuals. In some specimens the transition begins in the second 

 pair of cicca, in others it takes place farther back. There is no 

 abrupt line where gland cells end and absorptive cells begin, like 

 the sharp line between the end of the (esophagus and the beginning 

 of the stomach, but the gland cells and their companion support- 

 ing cells gradually become less numerous and are replaced by the 

 absorptive cells that belong to the middle intestine. Throughout 

 the course of the middle intestine, here and there are found gland 

 cells, fig. 34, Gl.i,, just like those of the stomach and the anterior 

 pouches. 



It is the presence of these gland cells, characteristic of the 

 stomach, in the anterior pouches and scattered through the rest of 

 the middle intestine, that has led me to believe that probably the 

 stomach and the middle intestine have a common origin from the 

 entoderm. The fact that there is not a well-defined histological 

 dividing line between the cell elements of the two regions, but a 

 gradual replacement of the gland cells by the absorptive cells, is in 

 confirmation of this opinion. And furthermore, to return to the 

 difterences between (esophagus and stomach, here we do find a 

 sharply defined and sudden transition from an epithelium resem- 

 bling that of the outside of the body to a truly glandular epithe- 

 lium; also, the opening to the stomach provided with a primitive 



