Intestinal Epithelium of Bufo Lentiginosus. 269 



The stomodeal septum is usually broken through on the sixth day 

 (larvae 11 mm. long). On the seventh day the coil is completely 

 formed and fills the whole ventral part of the abdominal cavity. 

 Figs. 23 to 25 show this stage in cross section. There is a low, 

 ciliated, columnar epithelium, having large nuclei at the proximal 

 end. The yolk is mostly absorbed, only an occasional cell being well 

 packed with small spherules. Rarely one finds a basal cell (Figs. 23 

 and 24), and in the distal border a mitotically dividing cell (Fig. 

 25). The sub-epithelial tissue forms a very delicate layer. Figs. 

 26 to 31 (two weeks after hatching) show the ciliated columnar 

 epithelium thrown into folds. Many mitotic figures appear at the 

 bases of the folds. These cells as a rule are clearer than those that 

 form the folds, — their appearance is suggestive of special activity, 

 perhaps of a grandular character. Bataillon ('91) noticed in the 

 epithelium of Alytes obstetricans, "a curious localization of karyo- 

 kinetic figures" at the bases of the folds. He suggests that perhaps 

 the irritation of compression causes activity at these points. 



Figs. 26, 27 and 28 show resting, spireme and anaphase stages of 

 basal cells, the first differentiation of the giant cells of Renter and 

 Duesberg. This stage is characterized by many mitotically dividing 

 cells in the distal zone of the epithelium (Figs. 29 to 31). A few 

 round cells appear (Fig. 31). 



Fig. 32 (three weeks after hatching) again shows the activity and 

 relative clearness of the protoplasm of cells at the base of a fold. The 

 other cells are well filled with fat, stained black with Flemming. Figs. 

 32 and 33 were made from larva3 which correspond approximately 

 to individuals I and II of Fig. 2, the hind legs having appeared. 



Histolysis. For the sake of clearness the histolytic phenomena 

 which now begin to appear in a marked degree, will be followed 

 through succeeding stages ; histogenesis will be considered later, al- 

 though the two processes go on side by side. Figs. 18 and 35 to 37 are 

 cross sections of N^o. Ill, Fig. 2. The cytoplasm still shows the fine 

 mottled appearance of the preceding stages, only rarely (Fig. 34) 

 showing small vacuoles and products of degeneration, brown and 

 yellow granules (Delafield and eosin stain). Fig 34 shows also one 

 of the many "round cells" which have now made their appearance. 



