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Some Observations on the Chromosome Vesicles in the Maturation ete.. 93 
the centrosomes. According to the degree of complexity of the 
changes which accompany this stage and the length of time required 
for the metamorphosis, the processes may be designated as the 
shorter or direct and the longer or indirecet. The shorter process is 
characterized by the chromosomes remaining free in the eytoplasm 
and by the direct formation of the achromatie figure; while in the 
longer process the chromosomes become enclosed in a so-called 
quiescent nucleus and the achromatie figure is formed indirectly.« 
As a rule the chromosomes in the first polar cell do not possess 
vesieles until after the division of this cell but an exception is re- 
presented in Fig. 10, where two of the chromosomes are enclosed 
but there is nothing to indicate that the remaining ones undergo a 
similar fate. 
Before the second maturation figure is fully formed, the chro- 
mosomes show important changes in the longer or indireet process. 
(The shorter or direet process is not described in this paper because 
it is so similar to the same phenomena in other Mullusca and many 
Annelids.) Each of the small chromosome vesicles with its contained 
chromosome looks like a minature nucleus. The chromosome is less 
prominent than in the previous stage (Fig. 10) and there exists 
definite linin threads between it and the containing wall. The 
early stages in these changes are indieated in Fig. 12. It may 
be noticed in passing that the marked spindle between the two 
centrosomes has disappeared, a phenomenon that will be fully con- 
sidered later. 
The conditions represented in Fig. 13, show the body that was 
the chromosome in Fig. 10, changed into one or possibly several 
small granules of chromatin Iying in the meshes of the linin. In 
the transition from this unusual state to a solid, large chromosome, 
the changes are the same as those which ocecur when the chromo- 
somes form from the germinative vesiele.e The chromatin granules 
increase in their staining capacity growing in the mean time until 
they are full sized again. As to the fate of the limiting vesicles 
two possibilities may be offered (s. ConkLis, p. 12), either they 
persist as indistinguishable sheaths or dissolve and loose their iden- 
tity in the eytoplasm. These fully re-formed ehromosomes lie in 
the equatorial plane of the spindle, divide, pass to the poles of 
the amphiaster, the egg chromosomes again passing, or forming, 
as is usual, into vesicles which sooner or later fuse to form the egg 
nucleus. 
