198 Harry Lewis Wieman. 



beginning in the larva and extending through the adult. The pro- 

 cess commences with accumulation of epithelial cells in the region 

 representing the lumen of the general cavity of the testis con- 

 tinuous with that of the sperm duct of the adult. The cells invol- 

 ved fragment, producing irregular masses which stain deeply with 

 the basic dyes. As the degeneration proceeds the area contracts 

 until in the adult it is represented by a concavo-convex disc- 

 shaped region marked off from the neighboring parts by a connec- 

 tive tissue capsule. The process is regarded as a method of pro- 

 viding nutritive material either for the spermatozoa or for the 

 germ cells during the maturation period. Thus the cells that 

 undergo degeneration are looked upon as the nurse cells of the 

 testis. 



Amitosis 



The occurrence of amitosis at corresponding stages in the germ 

 cells of both sexes is believed to be due to a periodic fluctuation in 

 the nutritive supply of the cells brought about by a stimulus to 

 a rapid cell division which causes a temporary derangement in the 

 normal metabolism. In the ovary the disturbance is merely 

 transient; but in the testis it is more prolonged for the reason 

 apparently that it is here involved in the formation of cysts, a 

 process that in the species under consideration is always accom- 

 panied by rapid cell multiphcation. 



In the nurse cells the initial cause of amitosis is probably the 

 same; but in this instance it is carried to an extreme, so that a 

 permanent change in metabohsm occurs. 



Amitosis and mitosis are believed to stand for the extremes of a 

 continuous series; the different configurations of the division 

 figures being due to the different types of metabolism represented. 



The Chromosomes 



The first spermatocyte spindle at metaphase, shows the pre- 

 sence of sixteen bivalent chromosomes that divide in this divi- 

 sion, and a bivalent V-shaped body, made up of equal parts, that 

 does not divide but passes entire to one pole. 



