49 
On Pallavicinia decipiens , Mitten. 
doubt whatever, In which, just before the exit from the centre, 
a further doubling of the chromosomes occurs, so that in 
reality four of these bodies, and not two, as I previously 
supposed, go to form the nucleus of each spore. The whole 
process Is very much crowded up, the four-rayed spindle 
persisting to the end ; and even after the exodus of the 
chromosomes, traces of it can still be seen, converging to the 
original centre. Moreover, so late is the whole process, that 
the sculpturing which characterizes the walls of the mature- 
spore is well advanced before nuclear division is even incepted. 
In many cells, the retreating chromosomes could be traced, 
but there nearly always appeared to be only two : this how- 
ever arises from the fact that I only saw them in profile, and 
not from the pole, and hence the two nearer ones covered the 
pair lying below. However in the young nuclei of the spores, 
whose walls have not as yet been formed to meet in the 
centre, the four chromosomes could sometimes, though with 
difficulty, be made out. The archoplasm, which forms the 
spindle, breaks asunder, and each arm contracts up along 
with the young nuclei, thus forming a sort of sheath around 
them, like that which surrounded the original mother-nucleus. 
The spores become finally separate by the appearance of 
membranes which complete the isolation of their contents in 
the centre of the tetrad, an isolation which is however nearly 
effected by the earlier ingrowths mentioned above. 
Now these features attendant on spore-formation in 
Pallavicinia are so abnormal, or at least depart so widely 
from our ordinary notions of cell-division, that I deferred 
publishing them until I should have had the opportunity of 
comparing it to the process as it obtains in other Hepaticae. 
I have examined the process in a number of other genera, and 
am still engaged in extending the observations, which will be 
brought together in a future communication. In this place 
I will only refer briefly to these results in so far as they help 
to elucidate the case of Pallavicinia. If the process be 
followed out in Aneura multijida, a form which is abundant in 
this country, essentially the same phenomena are perceptible, 
E 
