THE ORIGIN AND DEVELOPMENT OF GASTRIC GLANDS. 87 



Amblystoma, forming groups of two, three and four cells (Figs. 

 24, 25, a). While in both the other cases the epithelium was 

 relatively thick, here it is very thin. For, as the gland anlages 

 divide and increase in size, the epithelial cells gradually lose their 

 stratified appearance, and become arranged in a single layer. The 

 nuclei, instead of being arranged at different levels (Fig. 24, a), 

 assume their place in the center of the cells (Figs. 28, 29, cp}. 

 Before this process is completed the gland fundaments cause a 

 displacement of the surface cells, as in Desmognathus (Figs. 25, 

 26, </). The cells of the gland are arranged around a central 



. 



.V s -:-- ...:... 



\ : t 



' r N .' '. -*i\-'-\ 'yT- *" ' .1 



FIG. 24. Cross- section through the stomach of a pig of 62 mm. length. Fixed 

 in mercuric chlorid. ., "ovoid cells" or gland anlages; </., insinking to form the 

 duct; m., connective tissue to form the submucosa. The muscular layers are not 

 shown in any of the drawings of the pig. Obj. j 1 ^, Oc. 2. 



lumen, small to be sure, but still a lumen (Fig. 26, /). There is 

 also a slight indentation at the surface, as the cells are forced out 

 of their original position (Fig. 24, ^). Thus in an embryo of 

 6.2 cm. length (Fig. 25, d} there is a stage similar to that shown 

 in DesmognatJius and Amblystoma (Figs. 3, 20, d). The in- 

 sinking resembles that of Amblystoma rather than Desmognathus, 

 as it is merely a 'shallow pit. This deepens as the gland funda- 

 ments increase in size and the connection between the fundus and 

 the duct is then established (Fig. 27, ;/). Immediately after the 



