Nuclear Division in the Hepaticae. 501 
is, one of its poles is directed (apparently) into the cavity of 
a lobe, while the other is seen to terminate about a partition 
between the two lobes. And if the spindle end which 
occupies the latter position be regarded carefully, it will 
become obvious that it may sometimes fork, and that each 
limb of the bifurcation ends in an adjacent lobe. This is 
shown in PL XVII, Fig. 43. The apparent termination of 
the opposite end of the spindle in one point is, I believe, due 
to the fact that one sees the bifurcating limbs lying exactly 
one above another ; that is, it is in reality similar to the 
lower end, but the limb which enters the fourth cell lies in 
the same vertical plane with its fellow. Thus it seems clear 
that the apparent bipolar spindle here is the result of a more 
or less complete coalescence of four original protuberances. 
I am strongly of opinion that the spindle here produced 
is* of nuclear origin. During the quadripolar condition the 
chromatin is seen to be distributed in the form of eight little 
aggregations, much like those in Fossombronia. These little 
aggregations (Figs. 41 and 42) are the rudiments of the future 
chromosomes, and there can exist no doubt but that these 
bodies form closed rings ; when they are mature they take 
up a position just beneath the nuclear wall, and flatten out, 
so that they soon appear as mere rods. After the dis- 
appearance of the nuclear wall, they lie with their long axes 
directed along the spindle, and they then split across the 
middle as shown in Fig. 46. The daughter-chromosomes 
move apart, and a cell-plate is formed, which ultimately 
forms a membrane dividing the spore-mother-cell into two 
parts. Each of the two daughter-nuclei then divides once 
again, and the process is, so far as I have been able to follow 
it, an exact repetition of the first mitosis. Both of these two 
divisions are then heterotype. 
Cephalozia bieuspidata. 
The stage in this plant where a quadripolar spindle might 
have been expected was not observed, but during the first 
mitosis the forked spindle so nearly resembles that of Sea- 
