R 
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It may be said in criticism of this view, that none of these authors 
have given convincing evidence to show that there is a complete de- 
generation of the spermatogonia during these stages. It was assumed 
from the presence of numerous degenerating spermatogonia, that all 
would eventually degenerate. In some cases, individual seminiferous 
tubules seen in transverse section revealed no spermatogonia. No 
statement was made by any of these authors, however, to show whether 
or not these individual seminiferous tubules were consistently followed 
through a series of sections. It would, of course, be necessary to do 
so in order to exclude the possibility that adjacent portions of the 
same tubules might contain spermatogonia which would eventually 
furnish them to those portions without them. Again, I have myself 
in my work upon the mammals, found that it is, in certain stages, im- 
possible to clearly distinguish between the smaller spermatogonia and 
the vegetative cells. It is quite possible that these authors have seen 
many of the smaller spermatogonia during these stages, without being 
able to distinguish them from the vegetative cells. Degeneration of 
spermatogonia appears to be especially prevalent during periods of 
most active division. In the absence of any statement as to the exact 
extent of this process of degeneration, and judging from my own ob- 
servations upon the testis of the rabbit, I am led to doubt whether 
it is after all so extensive as these authors seem to consider it to be. 
In the mammalian ovary, there is an enormous amount of degeneration 
of the oögonia and oöcytes in both embryonic and post- embryonic 
periods, yet no one has ever claimed that they all disappear. A good 
account of this degeneration is given by v. WINIWARTER 700. He says 
of it, “c’est un phenomene commun a l’ovogenese et a la spermato- 
genese”. 
There is certainly no evidence of complete degeneration of the 
spermatogonia in Chrysemys. It is true that they can be found in pro- 
cess-of degeneration in all stages examined after that of car. 25 mm, 
but it is not all extensive. Here and there one finds a degenerating 
spermatogonium, while the surrounding ones are wholly normal. The 
normal spermatogonia are throughout in an overwhelming majority over 
the degenerating ones. The stages upon which these observations were 
made are — car. 26 mm, car. 50 mm, car. 73 mm, and car. 90 mm, 
together with a number of adult tests taken at different times of the 
year. These stages seemed to me amply sufficient to prove the con- 
tinuity in the chain of development of the sex-cells during these periods 
of pre-adult life. It was not until too late to gather new material, 
that this objection was brought to my attention. It is, however, very 
