462 
J. GRAY. 
cally all the chromosomes in some eggs of series F show a 
distinct tendency to form vesicles (hgs. 56-60). Every 
gradation is found between typical rod-like chromosomes and 
large well-formed vesicles^ and there can bcj therefore, no 
doubt whatever that these bodies are formed from the chromo- 
somes after the nuclear membrane breaks up. This is sub- 
stantiated by the fact that it is only the exception to find 
vesicles within the membrane of the fused male and female 
pronuclei. Fig. 53 shows such an exception. 
Besides the formation of numerous vesicles many mitoses 
show that there is a tendency for the chromosomes to be 
aggregated together in clumps, in some cases giving rise to 
irregular masses of chromatin (fig. 58). 
Chromosome counts in the anaphases of these eggs, shows 
that the formation of the vesicles has reduced the number of 
the chromosomes, as would be expected from their mode of 
formation. In all cases counted it was found that 32 to 34 was 
the average number for each group, together with a varying 
number of vesicles. If we regard, as before, each vesicle as 
ecpiivalent to a chromosome removed from each group of the 
anaphase in which it is fonnd, then the number of chromo- 
somes present, plus twice the number of vesicles, should 
give 76 units (cf. figs. 70, 71). This is sometimes the 
case, but numerous exceptions have been found, in which 
the aggregate is only 74 or less. But as in many 
cases the large vesicles in anaphases are exceedingly lightly 
stained (cf. fig. 61), it seems reasonable to suppose that in 
some cases they disappear altogether, the only evidence of 
their previous existence being the reduced number of the 
chromosomes. It is also possible that one vesicle may be 
formed from more than one chromosome, as is suggested by 
the shape of the vesicle in fig. 53 (cf. also the last vesicle 
fig. 47). 1 
^ Tlie low value of some of these chromosome coiants is doubtless to 
be explained by wrong interpretation as a single unit, of what is really 
two chi'omosomes closely approximated together. This approximation 
of chromosomes is characteristic of this series of eggs. 
