364 
Note. 
double division of the nucleus occurs within it, with no attendant 
formation of cell- walls. The four nuclei which have arisen in this way 
take up equidistant points near the periphery, and a tetrahedral 
division of the entire cell then occurs. The original spherical ( Riccia , 
Riella , Targionia , Marchantia , Plagiochasmd) or flattened ( Fegatella ) 
contour of the spore-mother-cell is retained until the spores separate. 
There are two specially important features which are characteristic 
of the karyokinesis of the spore-mother-cell. First, that the number of 
chromosomes is in every case reduced to one half, as compared with 
the antecedent mitoses in the sporophyte ; and that this reduced 
number is thenceforth retained in at any rate all those mitoses in the 
gametophyte which I have been able to feel confident about. Secondly, 
that the mitosis resulting in the formation of the spores differs from 
all the archesporial and vegetative mitoses in its character, and 
conforms to that type which Flemming distinguished as ‘ Heterotypic.’ 
A third feature of some interest, and which in practice is specially 
noticeable, is that, just at the period of the spore-formation, it becomes 
exceedingly difficult to fix the cells without contraction. This is the 
more remarkable, since the nuclei which may happen to be dividing 
in either earlier or in later stages, present not the slightest difficulty. 
Moreover the cytoplasm also stains deeply with most nuclear stains, 
and everything points to the conclusion that there is something going 
on in the cell during this so-called ‘ reduction-division/ which is not 
met with at any other period, whether in resting or dividing cells. 
The above points are only intended to indicate the general results 
at present obtained during these researches. The details, together 
with a general discussion on them, will shortly be published in extenso 
in this periodical. 
J. BRETLAND FARMER. 
Royal College of Science, 
London. 
