170 



Harry Lewis Wieman. 



to detect the process. In the testis it is more readily discovered, 

 for here, even in the adult, when the organ is packed full of sperma- 

 tozoa, amitosis can be seen among the spermatogonia lying in the 

 cap-shaped region opposite the point where the sperm duct leaves. 

 Many of these cells have not yet been grouped into cysts, and all 

 graduations between this condition, which is really characteristic 

 of the larval stages, to well defined cysts, can be found. 



sjig da 



Fig. Z. Diagram of longitudinal sections showing four stages in the develop- 

 ment of the testis. A, larva; B, larva two days older; C, pupa; D, adult, d. a. area 

 of degeneration; sp. d. sperm duct; spg. spermatogonia, filling cap-shaped region 

 opposite the mouth of the sperm duct; spz. spermatozoa. 



In the examination of a large number of sections of the adult 

 testis, I was surprised to find in all of them certain definite regions 

 in which degeneration of cells occurs. Further study showed that 

 the phenomenon is a regular event in the development of the or- 

 gans. (I have yet to discover a testis in which it is not found.) 



