Nttclear Division in the Hepaticae. 487 
the young chromosomes. In the absence of the early stages 
of the second mitosis it is impossible to be sure whether it 
conforms in general characters with the homotype form 
met with in the gametophyte, or whether it rather should 
be regarded as a second heterotype. There would be nothing 
strange in the recurrence of this latter form, since it certainly 
reappears in the successive spermatogenetic mitoses in many 
animals. 
After the chromosomes have receded to their respective 
poles the cell-plate now formed is converted into a cell-wall, 
and thus the division of the spore-mother-cell is completed. 
Very shortly after these events, changes become visible in the 
outer and common wall of the spore-mother-cell. It becomes 
extremely thin, except at those parts where the lobes were in 
close contact, and in the meanwhile the inner, newly-formed 
coat begins to exhibit the spiny character which is met with 
in the mature spore. The peripheral parts of the membrane 
become more and more attenuated, and finally disappear, but 
the thickened portions which lie in the angles formed by the 
lobes persist for a time, and sometimes break away and are 
found lying free amongst the spores. The separation of these 
bodies is effected by the final disappearance of the primary 
division wall 1 , but the period which elapses before this occurs 
is subject to some variation. 
After the complete formation of the spores they may either 
rest for a time within the sporogonium, or they may proceed 
at once to germinate. And in the latter event the process 
may even commence before the separation of the spores from 
one another (Fig. 28). 
The first sign of change is seen in the nucleus and surround- 
ing protoplasm. Beautiful centrospheres 2 with abundant radia- 
tions appear on opposite sides of the nucleus, which is rapidly 
drawn out in the direction of the longest axis of the spore. 
1 This agrees with Strasburger’s statements, Zellbild. und Zelltheil., dritte 
Auflage, p. 157. 
2 Cf. Farmer and Reeves, On the occurrence of Centrospheres in Pellia epiphylla. 
Annals of Botany, Vol. viii. 
