The Nucleolus and Microchrouiosomes in the Spermatogenesis etc. 183 
difler in auy way from those of the cells in the soma, it is better 
to eniphasise this similarity by giving no special name to the divi- 
sions which take place in the spermatogonia. 
The resting spermatogonium (Fig. 1) has a very homogeneous 
cytoplasm, with hardly any trace of the fibrillär structure which he- 
comes so distinct in the later stages, especially in the 2nd. meiotic 
division. Occasionally there is seen an archoplasm , which is only 
faintly stained with acid dyes. The nucleus is large in comparison 
to the whole cell, and contains a well-defined nucleolus, staining as 
heavily in this stage as any of the chromatin masses in the nucleus. 
The chromatin masses imbedded in the linin reticulum are not very 
numerous, hut are large. A few smaller masses, mere granules al- 
most, are also seen in the linin network. 
The changes up to the formation of the spindle do not differ 
from those already described by various authors in a host of other 
animals. 
A spireme is gradually formed (Figs. 2 — 4) and the nucleolus 
becomes fainter. At no time has the spireme the appearance of a 
single continous coil, hut rather is composed of many separate 
threads, connected together at the commencement hy very fine ex- 
tensions of the linin, which eventually disappear altogether (Figs. 4 
and 5). 
It was not possible to count these threads and see if they agreed 
with the numher of the somatic chromosomes, which is 30. 
Eventually the threads shorten up very much, and thicken slightly, 
and the nuclear membrane disappears (Fig. 6). The somatic spindle 
stains very faintly, so much so in fact, that I have never heen able 
to see it in the late prophases. 
The nucleolus has generally disappeared entirely at the middle 
prophase, hut it has very often done so, long before the spireme is 
definitely formed (Fig. 3). 
Ist. meiotic division. 
There is no resting stage after the final spermatogonial division, 
for immediately on the completion of the new nuclear membrane, 
the chromosomes separate apart (Fig. 8), and spreading over the 
linin network, assume the form of irregularly shaped chromatin 
masses (Fig. 9). 
These masses, each of which undoubtedly represents one somatic 
chromosome, are next arranged in pairs (Fig. 10). The numher of 
