284 WILBUR WILLIS SWINGLE 
changes of oocytes, such as leptotene, pachytene, and diplotene, 
before undergoing degeneration. 
Rubaschkin ('12) confirmed the conclusions of Von Winiwarter 
and Sainmont that the cells of the first and second prohferations 
in the cat degenerate. In the ovary of the guinea-pig this same 
investigator observed a third proliferation of germinal cells from 
the germinal epithelium which occurs before birth and which he 
considers the source of the definitive sex cells. 
Firket ('14) using female chick material, showed that the pri- 
naordial germ cells pass through the first stages of maturation 
previous to oocyte formation, leptotene, pachytene, etc., enter 
the growth period and then degenerate. They all disappear in 
the chick fourteen days after hatching. The oocytes of the cor- 
tical zone (second embryonic proliferation) practically all degen- 
■erate, although he states that he cannot be sure that they all do. 
There is a new formation of germ cells in the cortical region, 
from cells derived from the germinal epithelium, and from these 
the definitive oocytes develop; but it is not improbable, at least, 
that a small number of the primordial germ cells are differenti- 
ated into definitive ova. One of the conclusions Firket ('14) 
draws from his work is of considerable interest from the stand- 
pomt of the results on the frog recorded here: 
II faut, done, morphologiquement parlant, considerer les gonocytes 
primaires des Vertebres comme etant un rappel phyolgenique des 
gonocytes definitifs des classes inferieurs, notament des Cyclostomes et 
des Acraniens. L'epuisenient gradual, clans la serie phylogenique 
des elements de cette lignee a necessite Tapparition, au cours de I'onto- 
genese, d'une seconde lignee de gonocytes, moins precoces (pp. 330, 331). 
Recently there came to my attention an abstract of a paper as 
yet unpublished by this same author. I shall quote the abstract 
entire because of the striking similarity of the conclusions of this 
author, to some recorded by myself in this paper, both independ- 
ently conceived: 
In the testis and the ovary of the chick there are two generations of 
germ cells: primary germ cells, which appear in very early stages, 
before the genital ridge is formed, and secondary germ cells, which are 
derived from the so-called 'germinal epithelium.' The former are 
able to become oocytes, or spermatocytes, but while most of them 
