GERM CELLS OF ANXJRANS 285 
degenerate, it is not possible to determine if any of them give rise to 
definitive germ cells, because at a certain stage it is impossible to dis- 
tinguish the former and the latter from each other. In the white rat 
(male) the same two generations occur, but primary germ cells degen- 
erate before they reach the period of growth and onl}' secondary cells 
become the definitive germ cells. That primary germ cells disappear, 
in the ontogenesis, earlier in mammals than in birds, seems to show 
that the}' must be considered as being cells in 'phylogenetic regression.' 
Two interesting papers by Kingery on the female white mouse 
show that the phenomenon of primordial germ-cell degeneration 
is found in the mouse, and perhaps even more important in this 
connection is the fact that certain degenerating cells of this prim- 
itive germinal line may undergo abortive maturation stages even 
to the formation of first polar bodies. 
This author ('14) in a study of the so-called parthenogenesis 
in the mouse found that the degenerating primordial germ cells, 
i.e., those of embryonic origin, undergo a degenerative fragmen- 
tation and may even form a first polar body and second polar 
spindle, and may even break up into fragments with or without 
nuclei in much the same fashion as described by me for the larval 
spermatocytes of the frog. It is interesting to compare the fig- 
ures in Kingery's paper with those of my own in degenerating 
spermatocytes. 
In a later paper by this same author ('17-' 18), evidence of 
the kind described for the cat by Winiwarter and Sainmont ('08) 
and Rubaschkin ('12), for birds and the white rat by Firket ('14, 
also '20), and the male mouse by Kirkham ('16) is presented. 
The first or embryonic set of germ cells in the female mouse pass 
through early maturation stages, leptotene, pachytene, and dip- 
lotene, enter the growth period of the oocyte, then degenerate. 
The second generation of germ cells arise from the germinal epi- 
thelium after birth and give rise to the definitive sex cells of the 
adult female. He says: 
The evidence shows that all these germ cells formed before birth 
degenerate and are resorbed, none of them developing into definitive 
ova. This degeneration takes the form of atrophy and resorption in 
some cases, but in others there may occur atresia folliculi; accompanied 
by the formation of a first polar body, and a degenerative fragmenta- 
tion of the egg-cells, simulating more or less closely a parthenogenetic 
cleavage. 
