The nuclear compoueuts of the sex cells of four species of cockroaclies. 489 
that the ehromatin nucleolus of tliese stages represents the ockl chro- 
mosome. Therefore, there is uo direct observational proof that au 
odd chromosome is present in the prespermatocvte stages, although 
the indirect evidence afforded by the fact that the spermatogonial 
chromosomes uuinber oue fewer thau the oögonial warrants the con- 
clusio'u that such is the case. 
d) The plasmosome of the spermatogonia. Iu the telophase of 
the secondary spermatogonia (cf. fig. 6 , a well formed plasmosome oc- 
curs either in the fibres of the mitotic figure, as in the case repro- 
duced, or eise iu the cytoplasm. Wlien the nuclear wall has been 
reformed in the daughter cells, tliis body is invariably excluded from 
the nucleus and remains in the cytoplasm (fig. 7) where it nltimately 
disintegrates. The plasmosome is carried as a whole into one of the 
daughter cells and has never been observed to divide. The relation 
of the plasmosome just described to that of the earlier stages is not 
clear. Iu differential stains, one may sometimes distinguish a 
plasmosome in the metaphase plate. The achromatic mass contaiuing 
the ehromatin nucleolus of the earlier stages has been spoken of 
already, but continuity between it and the plasmosome of the later 
series could not be established. Whatever its origin, the spermato- 
gonial plasmosome is not continuous with that of the earlier sperma- 
tocyte stages (figs. 7 and 8). 
2. The early growth period. 
a) The ordinary chromosomes. After the nuclear wall of the 
telophase of the last series of spermatogonia has been formed, the 
chromosomes begin to lose their compact form and gradually to cou- 
tract into long delicate threads scattered throughout the nucleus 
(fig. 7). Apparently these threads are composed of a single series of 
granules and this stage presents no evidence of a longitudinal split. 
The ^threads now become even more delicate (fig. 8) and become 
compacted (fig. 9) into a ball so that ultimately, the threads lie in 
a tightly massed condition (fig. 10). The dark appearance of the mass 
is not due to the increase iu size of the threads nor to a capacity 
for deeper staining, but rather to their compactness. 
Now a polarization of the threads sets in, in the course of which, 
they are thrown into loops (fig. 11), converging towards the centro- 
somes. This is the so-called "synizesis” stage which is well marked 
in this species for the ehromatin mass pulls away from the a-polar 
