I6O R. R. HUMPHREY. 



favorable conditions, of course, are imposed upon all cells of the 

 testis alike, without reference to their position in the organ. 



That cells in more advanced stages of spermatogenesis are 

 least able to withstand unfavorable conditions has been demon- 

 strated experimentally in other animals. Siperstein ('21), for 

 example, has found that in adult white rats subjected to inanition, 

 the more advanced stages of the germ cells are the first to undergo 

 degeneration. Moore ('24), in his study of testis transplants 

 recovered after one to seven months, points out that some 

 influence "prevents the building up of a completed epithelium 

 with differentiated spermatozoa; instead the cells near the stage 

 of differentiation either degenerate in place or are cast off into 

 the lumen of the tubule." In his report on the changes in 

 testes rendered cryptorchid by operation, Moore further states 

 that spermatozoa rarely are present in the tubules seven days 

 after operation ; later the remaining cells of the germinal epi- 

 thelium disappear, the cells persisting longest being those at the 

 periphery of the tubules: i.e., the spermatogonia. It would 

 appear, therefore, that in mammals, as in amphibia, the cells 

 first affected by departure from the normal conditions are those 

 most advanced in development. In the four Urodeles discussed 

 in the preceding pages, conditions become but slightly unfavor- 

 able, and only certain of the most advanced cells are affected. 

 A condition comparable to that obtained by Moore in mammals, 

 may, however, be obtained in Urodeles by subjecting the males to 

 inanition over a considerable period of time. The entire testis, 

 in such animals, may be reduced to a slender cord in which no 

 germ cells save primary spermatogonia remain. The lobules as 

 such may entirely disappear. This condition is somewhat 

 comparable to the extreme reduction of the mammalian testis in 

 cryptorchidism, save that in the mammal the reduced tubules are 

 persistent. 



In no t'rodele examined does germ-cell degeneration commonly 

 reduce more than a fourth of the testis to an appendage. One of 

 even this proportionate length is unusual. It is clear that 

 animals with an excessive degeneration of germ cells would 

 produce fewer mature spermatozoa than males not showing this 

 peculiarity. Such males would probably leave fewer offspring 

 than the male producing a greater number of functional germ 



