WILCOX: SPERMATOGENESIS. 27 
POSTSCRIPT. 
In the Bulletin of the College of Agriculture of the Imperial Univer- 
sity of Japan has recently appeared a paper by Kametaro Toyama (794), 
“On the Spermatogenesis of the Silkworm.” The author has arrived 
at conclusions whioh in part agree with my own, but in part are quite 
different. 
Like myself, Toyama was unable to find any longitudinal splitting of 
the chromatic thread in the prophaser of the first spermatocyte division. 
He gives the following account of the complicated series of movements 
of the chromatin during the prophases : “A nucleolus is generally seen 
in the network of linin and chromatin. . . . Most of the chromatin 
granules become collected to one side of the nucleus and form an irreg- 
ular mass, . . . become again separate from each other and arrange 
themselves along the radiating linin fibres, and the skein stage is thus 
obtained. . . . The chromatin granules scattered in the nucleus 
become again collected in the centre óf it, and present an irregular mass 
as before. . . . In a still later stage the chromatin granules again 
commence to separate from one another. . . . A little before the 
appearance of the centrosomes in sperm-mother-cells the chromatin 
granules . . . gradually collect here and there and assume ring-shaped 
structures.” 
Unfortunately tho author presents no satisfactory evidence for this 
series of changes. He may have seen all the stages which are enumer- 
ated above, but he gives no proof that they succeed one another in the 
order he has stated. In the earliest prophases Toyama finds the chro- 
matin in nearly the same condition in which I find it in Caloptenus, and 
just before the first, maturation division he finds the chromatin arranged 
in quadrivalent rings. The progress toward the ring stage is, according 
to his account, twice interrupted by retrogressive processes. One can- 
not easily conceive the purpose of these complications, and the evidence 
for such an hypothesis could never be conclusive without direct observa- 
tion of the process in the living condition. I know no reason why we 
might not arrange Toyama’s Figures 23-43 in one continuous series. 
All stages represented in those figures are very young, and the numerous 
intermediate stages between them and Figure 44 are not shown. The 
concentrated condition of the chromatin seen in the author's Figure 30 
seems to me due to bad preservation. 
I disagree entirely with Toyama as to the processes in the maturation 
