30 HARLEY N. GOULD 



ing reaction from spermatogonia and the young spermatocyte in 

 the same region. 



Similar stages of spermatogenesis are usually found grouped 

 together; and when the spermatogonial or first and s cond 

 maturation divisions take place, mitotic figures occur in groups. 

 Many developmental stages of both kinds of sperm are found in 

 a single follicle of the testis, however. There is very little dif- 

 ference in the amount of activity in widely separated regions of 

 the gonad. Examination was made of sections through posterior 

 follicles, middle part and anterior follicles in all phases of the 

 sexual cycle; in immature males spermatogenesis was found to 

 be slightly more advanced in the middle portion; but develop- 

 ment or degeneration affects the whole organ. 



History of the gonad from the male to the female phase 



A. Regression of the testis. The first sign of lessened activity 

 in the testis is the absence of some of the stages of spermato- 

 genesis. The later primary spermatocytes are almost always the 

 first to be missing. Many testes show spermatogonia, spermatids 

 and sperm, but no spermatocytes.' This seems to indicate that 

 the cessation of activity consists in the failure of the young 

 spermatocytes (which cannot be distinguished from spermato- 

 gonia) to undergo the growth period and acquire the leptotene 

 nucleus. It does not prevent the fully grown spermatocytes from 

 undergoing the maturation divisions and becoming spermatids, 

 apparently, for in ordinary cases degenerating spermatocytes of 

 the first and second orders are not seen. 



Correlative with the disappearance of the spermatocytes there 

 is a slight shrinkage of the testis away from the surrounding 

 organs. Sometimes this shrinkage occurs even while the sperma- 

 tocytes can yet be found; in fact shrinkage of the testis cannot 

 be taken as a proof of impending loss of the male condition, , 

 though always accompanying it. 



Later the number of spermatocytes becomes less and less, and 

 some of the remaining ones begin to stain diffusely; more open 

 spaces appear in the lumen of the gonad than formerly; the 



