CYTOPLASMIC INCLUSIONS OF THE GERM-CELLS. 431 
The centrosome is never, as far as I have ascertained, sur- 
rounded by a definite zone (archoplasm), and the structures 
mentioned by Dr. Cook are almost certainly the mitochon- 
drial granules. 
Though it is a matter of great difficulty, and I confess of 
some doubt, to detect these bodies (mitosome and centrosome) 
in the cytoplasm of the resting primary spermatogonium, 
their presence is indubitably confirmed when one examines 
spermatogonia in process of division. In PI. 23, fig. 2, is 
drawn a inetaphase from the side. On the left are the mito- 
chondrial granules (MD), while on the mid-right of the cell 
are seen two bodies marked M which are the micromitoso- 
mata. This figure, and the drawings in PI. 23, figs. 3, 9, and 
10 ; in PI. 24, fig. 18 ; in PI. 25, figs. 34 and 49, seem to show 
that this body does divide, and apparently in the early 
prophases of the cell division, but I found it very difficult 
to make sure. I never was quite satisfied that it really did 
divide, and the only confirmatory evidence is that found in 
my figures, above mentioned. Bearing in mind that it is very 
rarely that one finds more than one micromitosome in the 
spermatocyte, and that almost without exception every sper- 
matid has such a body, one is justified in concluding that 
this body really does divide. Apparently the micromitosome 
divides autonomously. Confirmation of this view is derived 
from the behaviour of the micromitosome in the spermatocyte 
divisions, mention of which will be made later. 
Reference may be made to PI. 23, fig. 3; PI. 24, fig. 21, 
which show these bodies in material fixed in strong Flemming 
in which the glacial acetic acid has been reduced. In this 
case the body does not stain so heavily ; spermatogonial 
mitoses show that the position occupied by the micromitosome 
is not definite. The most that can be said is that this body 
more often than not lies between the chromosomes and the 
equator of the spindle, rarely being found further towards 
the centrosome. 
During the growth period of the secondary spermatogonium 
and spermatocyte the micromitosome, which apparently has 
