Plate III. 



Fig. 21. Cross-section of Bufo tadpole, at the level of the pronephros, 5 

 days after hatching. Detail (z) shown in Fig. 22. x 80. 



Fig. 22. Duodenum, 5 days after hatching. Cross-section, x 990. 



Figs. 23-25. Duodenum, 1 week after hatching. Cross-section, x 990. 



Figs. 26-31, Duodenum, 2 weeks after hatching. Cross-section, x 990. 



Fig. 32. Duodenum, 3 weeks after hatching (like No. I, Fig. 2). Cross- 

 section. X 990. 



Fig. 33. Duodenum, from a tadpole like No. II, Fig. 2. Cross-section. 

 X 990. 



Fig. 34. Duodenal epithelium from tadpole No. Ill, Fig. 2. Cross-section. 

 Micr. Leitz. oc. 4, obj. im. Via. 



Figs. 35-37. Duodenum. Tadpole No. Ill, Fig. 2. Cross-section, x 990. 



Figs. 38-41. Stages of chromatolysis. Nuclei from duodenal epithelium of 

 tadpole No. IV, Fig. 2. Oc. 4, obj. im. V,j. 



