244 B. F. KINGSBURY AND PAULINE E. HIRSH 



study would hardly seem likely and it is far more probable thai 

 if such degenerations occur, they do so at a later season than that 

 studied by Miss King (i.e., after September), possibly at the be- 

 ginning of hibernation, when, if ever, one might expect a checking 

 of the spermatogonial divisions to be accompanied by degenera- 

 tions. Granted that these are 'physiological degenerations,' it 

 should be appreciated that there is no reason for believing that 

 the factors upon which they depend would be operative in all 

 forms in the same way. The degenerations might or might not 

 occur, which fact should be considered in making comparisons 

 between the processes taking place in the testis of the toad and in 

 that of the salamander where this may be particularly applicable. 



The lavish outlay of germ cells and their wholesale degenera- 

 tion has been commented on by a number of writers. There may 

 be particularly mentioned : Winiwarter and Saimont (mammals) , 

 Hoffman ('92), D. Hollander ('05) (birds), Bouin ('01), Dustin 

 ('07), Levi ('05) (amphibia). 



The descriptions of Winiwarter who has given the most mono- 

 graphic description of mammalian oogenesis are particularly 

 interesting. In the rabbit ('00) he described two epochs of de- 

 generations which were completely separated. Of these the first, 

 including typical and atypical karyolysis, is of particular interest 

 in this connection. The second occurred in the atresia folliculi. 

 Winiwarter found that the multiplication of the oogonia ceased 

 soon (about ten days) after birth. The degenerations of the first 

 epoch extended from the twenty-third day embryo nearly to 

 eighteen days after birth. The degenerating cells were found to 

 be, in the large majority of cases at least, oogonia which suc- 

 cumbed particularly at the time of their division. At what 

 point the karyolysis sets in he is not sure but he thinks that in all 

 probability it is at the equatorial plate stage. Comparison of his 

 results with the conditions in Desmognathus are quite suggestive. 



In the cat ('08) the degenerations begin to appear singly. In 

 embryos of forty-five to fifty days large groups of degenerating 

 cells are present. Shortly after birth the multiplication of the 

 oogonia suffers an arrest and, coincident with this, there is a 

 recrudescence of degeneration. The groups of nuclei particularly 



