THE EFFECTS OF HYPERTONIC SOLUTIONS. 
453 
In the daughter-nuclei of the first division thei’e are usually 
a few minute vesicles such as have been described for the 
male pronucleus — the fate and origin of these is unknown 
(fig. 16). 
Fig. 17 shows that there is a tendency for some chromo- 
somes to be omitted in the first division — the significance of 
this will be discussed later. 
In tripolar and tetrapolar spindles, which are often derived 
from a female pronucleus which has fused with more than 
one male pronucleus, there is only one vesicle (figs. 17 and 
17 a). 
The interest of these vesicles lies in the fact that they are 
exactly similar both in appearance and behaviour to those 
which have been described (Doncaster and (li ay [2]) for the 
h}'^brid eggs of the cross E. esculentus S ^ E. acutus ?, 
There is, liowever, one point of difference : in the hybrid eg”S 
vesicles were never found earlier than the prophase of the 
first division, i. e. until after the nuclear membrane had dis- 
appeared ; while in the eggs treated with hypertonic solution 
the vesicles are more numerous and distinct within the nuclear 
membrane than in any other phase of division. 
I’he origin of the vesicles in the hybrid eggs is described 
in tlie introduction to this paper, and is obviously different 
to that of the vesicdes in those eggs of E. esculentus which 
have been treated with hypertonic solutions. 
Considerable time lias been spent in an attempt to deter- 
mine by actual chromosome counts whether the large vesicle 
in these hypertonic eggs is morphologically equivalent to one 
chromosome. 'I'liis has not been altogether successful, as 
the crowding of the chromosomes makes it exceedingly difficult 
to determine whether their number is thirty-seven or thirty- 
eight. As, however, this vesicle is exactly similar in appear- 
ance and behaviour to those formed directly from the 
chromosomes, both in the hylnld eggs and in “hypertonic’^ 
eggs of E. acutus, 1 believe that this vesicle does represent 
a chromosome, and therefore regard it as being formed from 
that part of the nuclear network which normally goes to form 
