504 Transactions of the Society. 
component halves thus corresponds to fig. 51 in Miss Sargant’s 
paper, though it is obvious that our interpretations differ widely. 
2. Variations may occur, and of these it is impossible to mention 
more than a very few. The most frequent one is that in which the 
young mother-chromosome does not form a completely closed ring 
after the longitudinal fission has occurred. When it is closed at one 
but not at both ends, the free limbs often cross each other, and 
according as they do this more or less so will the further development 
of the chromosome be affected. If they scarcely cross, or do not do so 
at all, they may go through the same series of metamorphoses as have 
already been described. More often, however, the whole chromosome 
comes to be attached to the spindle by one of its ends, and most fre- 
quently by the end at which the two halves are free. The respective 
halves then diverge a little above the actual end of the chromosome, 
and so the incurved figure shown in Miss Sargant’s fig. 49 is pro- 
duced. In those cases where the original chromosome was attached 
to the spindle fibres at the middle of its length, the figure represented 
by Miss Sargant in her fig. 51 might probably occur, though I cannot 
accept the conjectured sequence of events as suggested in the text. 
Whether such a figure as that of 51 would be produced would, I 
think, depend on the original position of the chromosome on the 
spindle, and I have seen no evidence to suppose that such a form as 
that represented in fig. 49 would ever pass into that shown in fig. 50 
or 51. The relative length of the incurving portions which subse- 
quently separate bears no constant relation to the common undivided 
portion, and therefore I cannot admit that any conclusions, based on 
this relation, as to the age of the chromosome, are valid. 
In those cases where the free ends of the longitudinally split 
chromosome cross each other to a large extent, the body commonly 
becomes attached to the spindle at the point of crossing. As the ends 
are already curving outwards, this peculiarity becomes accentuated as 
the division of the chromosome proceeds, and in this way many of the 
forms with outcurving limbs (see fig. 48, c in Miss Sargant’s paper) 
may be accounted for. That this is really the case may be easily 
decided, as one limb may be seen to be actually lying across the other 
until quite late in the entire process. This particular type often gives 
rise to very singular forms : sometimes the daughter-chromosome 
remains nearly straight along the spindle, and the two are still 
attached to one another by a knot-like swelling at the middle. When 
this gives way very late, the phenomenon is seen of a chromatic 
thread extending through the whole length of the spindle from pole 
to pole. These figures are, however, rare. 
From what has been said it will he obvious that, in the heterotype 
as well as in the homotype form of division we have a longitudinal 
fission of the mother-chromosome, but that in the former the process 
is greatly complicated. I may mention that in some Liverworts 
which I am at present investigating, the homotype division may be 
more complex than usual, and even approximate to the heterotype in 
character. 
