Nuclear Division in the Hepaticae. 519 
animals is opposed to such hypothesis, for in animals no 
4 reduction ’ is claimed at this stage. Moreover it seems 
clear that whatever significance the heterotype form of mitosis 
may possess, it cannot be concerned with a qualitative reduc- 
tion, since in animals 1 , and at any rate in some plants, two 
heterotype divisions succeed each other, and there is no reason 
for supposing that the real process is so essentially different 
in the two cases as to effect a reduction in the one and not in 
the other. 
Thus it would seem that the heterotype divisions in plants, 
different as they are from the normal homotype mitosis in the 
rest of the cells of the organism, afford no evidence in support 
of any assumption of a qualitative difference existing between 
the daughter-chromes in each pair. The only 4 reduction ’ is 
a numerical one, and it would appear that this must be due 
to an end-to-end fusion in pairs which occurs in the resting 
nucleus, as was suggested by Strasburger 2 * ; that is if the 
chromosomes really retain their identity in the resting nuclei. 
But it is difficult to feel certain even on this point. Certainly 
the chromatin as such does not remain unaltered. It under- 
goes chemical change during the last phases of karyokinesis, 
which results in the loss of staining power and a large portion 
at least of its substance. Prof. Strasburger has recently 
suggested that the chromatin wanders into the nucleus from 
the cytoplasm in a dissolved condition, and he explains the 
c Sichel-stadium,’ previously described by himself and other 
authors under different names, as a condensation of this 
substance at one end of the nucleus. It is driven here 
owing to the one-sided penetration and diffusion of the re- 
agents used in fixing. It is, however, not very easy to see 
how such a quantity of dissolved chromatin could exist in the 
nucleus without colouring the nuclear sap in those cells in 
which the fixing has succeeded better. But however this may 
be, it hardly seems to me to be probable that the chromatin 
1 Moore, loc. cit. 
2 On the periodic reduction in the number of the Chromosomes. Annals of 
Botany, Vol. viii. 
