Intestinal Epithelium of Bufo Lentiginosus. 271 



No. VII, Fig. 2) show the appearance of the final stage of degenera- 

 tion of the columnar and round cells and the manner in which they 

 are pinched off into the lumen when the final muscular contraction 

 occurs. The debris is given off through the anus. Duesberg suggests 

 that some of it may be absorbed as nourishment. 



Histogefiesis. At the stage represented by No. Ill (Fig. 2) many 

 giant cells can be distinguished in the duodenum (Figs. 18 and 35 

 to 37). Owing to the fact that a giant cell, as it now becomes active, 

 takes a diffuse deep blue stain, with haematoxylin, it can be easily 

 distinguished, even when it has but one nucleus, and more readily 

 when there have been repeated mitotic divisions and a syncytium 

 or a cyst has been formed (Fig. 18, g. c). Figs. 35, 36 and 



42 show stages in the formation by mitosis of the syncytium and the 

 characteristic appearance of the nuclei, large and plump, with fine 

 chromatin network and large nucleolus. These nuclei and the small 

 amount of deeply staining cytoplasm in which they are irregularly 

 massed (Fig. 42) soon form a cyst, a hollow sphere, which breaks 

 open on the side toward the lumen of the alimentary tract (Fig. 43), 

 This condition corresponds to that found in Alytes obstetricans. In 

 Rana fusca the developing epithelium does not go through a cyst 

 stage, — the syncitia appear as scattered patches of new epithelium, 

 which meet and fuse when contraction occurs. This broken cyst 

 opens more widely (Fig, 44), and at the same time the nuclei become 

 oriented, with their long axes parallel to one another. Cell walls 

 appear and a cuticular border is formed. Eventually these isolated 

 crypts of new epithelium become joined edge to edge (Fig, 16) ; 

 thus the continuous, definitive epithelium is formed (Figs. 17 and 

 45). As the process of histogenesis is progressive from stomach to 

 rectum, it was possible to find these two last stages (Figs, 44 and 

 45) in the same individual (No, VII, Fig. 2). 



The new epithelium forms much earlier, in comparison with the 

 progress of degeneration, in Bufo than in Alytes (compare Fig. 



43 with Renter's Fig. 38). 



This account of the histological changes which occur in Bufo 

 agrees, I believe, in the main with that given by Duesberg for Rana 

 fusca. It has been limited chiefly to a statement of the facts, because 



