THE EFFECTS OF HYPERTONIC SOLUTIONS. 
461 
as essentially chromatic in nature. If this be so^ however, it 
is remarkable that two nuclear elements of such widely 
different origin should appear so exactly similar. It seems 
more probable that those vesicles which are formed within 
the nuclear membrane are formed from those parts of the 
network which normally enter into the composition of one or 
more chromosomes, as is suggested elsewhere in this paper. 
Series C. — E. acutus eggs treated w'ith 50 c.c. sea-water 
-F 7 c.c. 2.^ M. XaCl solution. 
In preparations of these eggs no vesicles have been found. 
The clu’omosomes are, however, somewhat irregular, as they 
show a marked tendency to group themselves together. On 
account of this, accurate determinations of their number is 
usually impossible, but in some case the full somatic number 
can be counted. In anajihase plates it is remarkable that 
many of the chi-omosomes appear double (cf. fig. 67). 
Usually the mitoses are somewhat irregular, and in some 
cases there is a marked omission of chromosomes from the 
main groups, as shown in figs. 67 and 68. Fig. 69 shows a 
condition very similar to Baltzer’s (1) figs. 25 b and -33 a of the 
firstsegmentation division of Sphaarechinus c5' x Strongy- 
locentrotus ? and the second division spindle of Echinus 
? X Sphaerechinus c? respectively. 
Another peculiarity in these eggs is that the spindle is very 
much narrower than is normal for this species of Echinus 
(fig. 51), in fact the spindle in this series of eggs recalls the 
narrow spindle of the hybrid E. miliaris x E. acutus ? . 
Is it possible that the narrow spindles of this hybrid are 
a result of abnormal conditions due to hybridisation, and are 
not a characteristic feature of the male parent ? (The spindles 
ofE.miliaris $ x E. miliaris are broader than those 
of the hybrid eggs.) 
Series F. — Eggs treated with 50 c.c. sea-water -F 15 c.c. 
24 M. NaCl solution. 
Ill this series of eggs the process of vesicle formation is 
still more pronounced than in series B. There are, however, 
one or two poiuts of distinction between these series. Practi- 
