584. L, DONCASTER. 
the view that maleness and femaleness are of the nature of 
molecular forces, which are mutually attractive, or which 
cause an attraction between bodies bearing them, just as 
opposite poles of a magnet or bodies charged with positive 
and negative electricity attract one another.! If these two 
hypothesis are combined it may be supposed that in the 
male-producing sawflies, such as N. ribesii, the four nuclei 
which result from the second polar mitoses are alternately 
male and female bearing, i.e. are arranged in order from 
within outwards, as in Diagram 1: 
Diacram 1. 
Inner. Outer. 
6 die OBS Maas 
cS seal ane 
there will then be an attraction between the two inner polar 
nuclei, which will cause them to move together and fuse. 
The nuclei of the female-producing species may be imagined 
to have two male-bearing nuclei in the middle, and a female 
at each end (Diagram 2), 
Diacram 2. 
Inner. Outer. 
8 Sie: Fae 6 eee 6 
ne ea lee 
in which case there would be no attraction between the inner 
polar nuclei. ‘lhe question at once arises, ‘‘ Why do not the 
daughter-nuclei derived from one mitosis move together and 
fuse again if they bear opposite sexes?” But it is evident 
that the force which brings a mitosis about, and drives the 
chromosomes to opposite ends, is a different force from that 
now imagined, since it occurs quite apart from sex, and it 
may be supposed that the force which causes the chromo- 
somes to separate remains sufficient to keep the nuclei from 
coming together again. But that this may cease to operate 
1 FB, Le Dantec, ‘ Traité de Biologie,’ Paris, 1908, pp. 154—166, 
