1 62 
Davis . — Nuclear Studies on Pellia. 
The division of the chromosomes and their arrangement 
during metaphase of the two mitoses in the spore-mother- 
cell presents features well known to cytologists. Farmer 
described the first mitosis in several Hepaticae as heterotypic. 
The writer found no evidence of such conditions in Pellia. 
The chromosomes split longitudinally and, as they separate, 
present various figures in both mitoses according to the 
position at which the fibrillae are attached. Figs. 19 and 
10 show the commonest manner of attachment and separation, 
the twisted daughter-chromosomes being pulled apart from 
their ends. Very much less frequently the fibrillae are 
attached in the middle region of the daughter-chromosome as 
in Fig. 20, and the elements might then present the form of 
a ring as they are drawn apart, which arrangement would 
be heterotypic. But the daughter-chromosomes are so much 
like short rods that there is little opportunity for complexity 
of arrangement at the time of separation, and the V figure 
prevails. 
The chromosomes at the metaphase of mitosis are homo- 
geneous in their make up, no granules being distinguishable 
in the structure, but a change comes over the elements during 
anaphase, and while the daughter-nuclei are being organized. 
The chromatin-droplets appear again in an irregular row 
(see Fig. 21), on the variously bent rods which shortly begin 
to fragment. In this manner the droplets of various sizes are 
set free in the interior of the daughter- nuclei (see Figs. 12 
and 16). 
We now pass to the consideration of the mitoses found in 
the germinating spore. This is a most interesting period 
in the life-history of Pellia , one very favourable for the study 
of nuclear phenomena, and most so during the first and 
second mitoses. The nuclei presented in later stages of 
* germination are very much smaller, and peculiarities found 
at first are inconspicuous then. A paper by Farmer and 
Reeves (’ 94 ), ‘ On the occurrence of Centrospheres in Pellia 
epiphyllaf dealt with this period of ontogeny. They found 
centrospheres with radiations outside of and touching the 
