THE EFFECTS OF HYPEJri'UNlC SOLUTIONS. 
471 
I'emarkably similar, they are fiindanientally different, as he 
never observed any elimination of chromatin from the 
nucleus. 
In the introduction to this paper, a short description was 
given of the cytology of the hybrid eggs of Echinus acutus 
$ X E.esculentus cJ. It has now been shown that the 
phenomena observed in this cross can be exactly paralleled 
by the effects of hypertonic solutions upon the eggs of E. 
acutus, and that similar treatment affects E. esculentus 
in a different way. 
A conclusion which may, therefore, be made is that the 
cytological phenomena of hybridisation are, in fact, the phe- 
nomena of pathology, and that, when an egg is fertilised by 
the sperm of a foi’eign species, the behaviour of the male and 
female chromatin tends to become irregular, owing to a general 
derangement of the whole nucleus, elimination, therefore, 
cannot be regarded as a simple rejection of that part of the 
nucleus which is out of tune with the rest, or with the cyto- 
plasm of the egg. 
In other words, we must assume that, whenever the condi- 
tion of the nucleus becomes peculiarly abnormal, certain of 
its constituent elements are affected to such an extent that 
they are no longer able to pass through their normal phases, 
and, therefore, fail to take part in the further development of 
the cell; thus, in the case of the chromosomes, some are, ap- 
parently, more affected than others, and are eliminated from 
the nucleus. 
The bearing of these results upon the cytology of the 
leciprocal hybrids of the species of Echinus is more fully 
de.sci’ibed in. another paper (Doncaster and Gray [2a]). 
VII. d’HEORETICAL. 
Until recently, it was supposed that the cell-membranes in 
animal tissues were practically impermeable to electrolytes. 
It has now been shown that this is not the case, and con- 
i-iderable evidence is available to support the opinion that the 
