Nuclear Division in the Hepaticae. 517 
so that I need do no more here than briefly recapitulate the 
important steps of the most normal type met with, bearing in 
mind, however, that variations on this may occur \ The 
process, in outline, is as follows : The chromosomes in which 
the longitudinal fission has taken place, and which may be 
open or closed at both ends, doubles on itself. The two sides 
now begin to divaricate, beginning to do so at the place where 
the bending occurred. Thus the well-known T shape is 
produced, the vertical bar of the T representing the hump 
which is produced by the approximation of the two ends of 
the young chromosome, and which are directed outwardly 
from the surface of the spindle. Finally, the two halves 
separate along the spindle, and as a result of the bending 
already referred to, the daughter-chromosomes have from 
the first the shape of the letter V ; each represents one of 
the original longitudinal halves of the mother-chromosome. 
Variations on this process may occur, but the essential feature, 
namely, the longitudinal splitting of the mother-chromosome, 
giving rise to the two daughter-structures, is common to all. 
The second mitosis in the spore-mother-cell of the liver- 
worts investigated is, so far as the minuteness of the objects 
admitted of its being traced, similar to the first, though the 
earlier stages were, however, exceedingly difficult to follow on 
account of the small size of the nuclei. On the assumption of 
a double splitting occurring during the first mitosis, it is 
obvious that the chromosomes in both divisions might well 
exhibit that identity in form which, as a matter of fact, is 
actually displayed. 
In this respect the second karyokinesis in the Hepatic 
spore-mother-cell differs from that one corresponding to it in 
Lilies. The dissimilarity between the two consecutive mitoses 
in the pollen-mother-cells of Lilies and some other plants is 
most striking, and has not escaped the notice of those who 
have investigated these plants. I think I am justified in 
asserting that in the second division of the pollen-mother-cell 
1 Ibid. 
