573 L. DONCASTER. 
In both N. ribesii and P. luteolum the number in both 
the polar mitoses is undoubtedly seven or eight, and if 
reduction takes place in the ordinary way this must be the 
reduced number. But in both species spindles of somatic 
nuclei in the yolk or blastoderm show clearly that the number 
is not changed; eight (or possibly seven) chromosomes go to 
each end of the spindle. It is evident, therefore, either that 
a doubling of chromosomes takes place at a later stage, or 
that no reduction can take place in the next generation. The 
maturation spindles are so small that the question whether 
reduction occurs is not easily answered, but I have seen no 
evidence of it. If, however, the pairing (pseudoreduction, 
synapsis) takes place just before the maturation divisions, as 
has been described in so many insects, then the chromosomes | 
at their first appearance in the laid egg would have the 
reduced number. Some of my sections of first polar spindles 
have a considerable resemblance to the figures given by Gross 
(3, Pl. 31, fig. 64) of the reduction divisions of Syromastes, 
particularly in the thickening in the middle of spindle fibres 
during the anaphase (fig. 1), but I have not been able to find 
any trace of tetrad formation or other evidence of normal 
reduction. 
And in this connection a point of great theoretical interest 
arises, for in P. luteolum, in which the mitotic figures are 
most clearly shown, the species is normally parthenogenetic, 
only females being produced. It has been maintained by 
Hacker (4), Sutton (12), Montgomery (8), and others that of 
each couple of chromosomes which pair together at the stage 
of pseudoreduction one is of paternal, and the other of 
maternal, origin. But in a species which is regularly par- 
thenogenetic there are no paternal chromosomes, and hence 
either pseudoreduction cannot occur at all, or it must take 
place in an abnormal manner. My comparison of the matu- 
ration mitoses with those seen in the blastoderm leads me to 
the view that no reduction takes place at any stage, and that 
all the divisions in this species are equation-divisions, and 
this view receives some support from the similarity of the 
