288 H. M. KINGERY 



Kingsbury ('13), while admitting that his material was too 

 scant to permit a conclusive statement, inclined to the opinion 

 that there was no evidence of a new formation of ova by a third 

 proliferation from the germinal epithelium of the cat's ovary. 



R. Van der Stricht ('11) apparently does not consider this 

 question at all, as, in his work on the vitellogenesis of the cat's 

 egg, he makes no mention of such a new formation of ova. But, 

 as he accepts von Winiwarter's terminology and course of de- 

 velopment for the egg-cells, and states, further, that oocytes with 

 diplotene or dictye nuclei are found in the adult ovary, it may 

 be assumed that he derives the definitive ova from the second 

 proliferation. 



Rubaschkin ('12) states that he can corroborate the conclusions 

 of von Winiwarter and Sainmont that the cells of the first and 

 second proliferations in the cat degenerate. He says nothing, 

 however, about a third proliferation, but one is led to infer that 

 in his opinion one does occur. He further states that Waldeyer 

 had described a proliferation of cells in the post partum develop- 

 ment of the ovaries of several animals, but I think Rubaschkin 

 has been misled. In the reference mentioned by him, Waldeyer 

 ('70) says that he believes there is no new formation of egg-cells 

 from the surface epithelium, but that any epithelial down-growths 

 present in post partum ovaries of dogs and rabbits are left 

 over from the embryonic proliferation. Moreover, he states: — • 



Audi bei Katzen, von welchen ich mehr.ere zur Zeit der Friihjahrs- 

 brunst untersuchte, fand ich, wie gesagt, Nichts von einer derartigen 

 Neubildung. Meine Untersuchungen sind so zahlreich, dass, wenn sie 

 wirklich vorkommen sollte, wir eine sehr seltene Ausnahme und am 

 allerwenigsten eine Regel vor uns hiitten. (70, p. 45). 



Rubaschkin also says that he found a third prohferation of 

 cells from the germinal epithelium of the ovary of the guinea pig 

 which occurs before birth and which he considers the source of 

 the definitive ova. 



Firket ('14) describes in the embryo chick a third proliferation 

 of cells from the germinal epithelium which he states forms the 

 most if not all of the definitive ova. As mentioned above, how- 

 ever, he is not able to state definitely that all the mature ova 



