Some Observations on the Chromosome Vesicles in the Maturation ete. 97 
seems to indicate that the vesicles which I have termed »chromo- 
some vesicles« are formed from the linin, the details of which pro- 
cess I have as yet not been fully able to solve. 
But whether the vesicles which oceur in H. solitaria are the 
lame as those in Orepidula and in Doris I have some doubt. That 
the vesicles found in Crepidula and Doris are the same there can 
be no question. The following may be said concerning the fate of 
these vesicles in AZaminea. The chromatin increases in quantity for 
a time but never completely fills the vesiele, a clear space which 
takes a plasma stain is always evident. At the time when the 
chromosomes have become full sized or as large as they do become 
while in the vesicles, there is no evidence of a shrinking of the 
walls or a diminution of the enclosed area; the only change being 
that the walls become less distinct. 
While this discussion must be tentative at this time as the facts 
are too few to warrant any definite conelusion, yet it is diffieult for 
me to see how these vesicles can persist through the subsequent 
maturation changes as an indistinguishable limiting membrane around 
each chromosome as suggested by ConkLın. But is seems to me 
rather that the walls of the chromosome vesicles disappear, simply 
fading away, probably being dissolved in situ. This leaves us with 
two suggestions. 1. That the linin sheath lies elose to the chromo- 
some and is evident only during division. COoNKLIN, p. 12. 2. That 
the chromosome vesicles in ZH. solitaria disappear in the cytoplasm 
being dissolved in situ. The origin of these vesicles in Doris 
will be further discussed in connection with the problem of fertili- 
zation. 
Centrosome. In describing this body the terms proposed by 
Boverı ('01, p. 32, 125) are used. The centrosome is the body in 
which the astral and spindle fibres terminate. At certain stages it 
is a highly differentiated body composed of a central granule, termed 
the centriole which is surrounded by an area designated the centro- 
plasm. The centroplasm usually takes a plasma stain while the 
centriole is always stained by haematoxylin. 
In the eggs of these three species of Nudibranchs no evidence 
of a centrosome was found before ovoposition had begun; nor was 
it possible to distinguish with certainty this body in a stage earlier 
than that shown in Fig. 2. In Figs. 2 and 3, the centrosome is a 
small, solid granule, undifferentiated. None of the stages indicate 
that this body is composed originally of more than one body as in 
Morpholog. Jahrbuch. 33. 7 
