572 L. DONCASTER. 
my own experiments were unsuccessful, since although the 
egos hatched the larve died off at an early stage. But the 
two species are so closely related in habit and structure that 
it seems very probable that both belong to the same group, 
and that virgin eggs of N.lacteus would produce males if 
the larvee were successfully reared. 
In both species the eggs are laid in large groups on the 
under side of the leaf of the willow; the group consists of a 
number of transverse rows of eggs, the eggs in each row 
lying side by side. 
In N. lacteus the maturation mitoses take place as in 
N. ribesii, and four nuclei arise lying in a line perpen- 
dicular to the edge of the egg (PI. 35, figs. 4, 13). The two 
middle ones, i. e. the second polar and inner half of the first 
polar nucleus lie from the first near together; they come 
into contact and apparently fuse as in N. ribesii. The 
fusion, however, does not seem to so complete-as in this 
species, for at a stage not many minutes older two groups of 
chromosomes are found lying near together in the polar 
protoplasm. One of these groups clearly consists of about 
eight chromosomes, but the other group is more irregular, 
and not so many can be counted (PI. 35, fig. 14). In some 
egos only one group of about eight is seen, and it seems 
possible that in some cases the two nuclei come into contact, 
but do not fuse, and that one of them breaks up into 
chromosomes, while the other merely degenerates. ‘his 
idea is supported by the fact that in some eggs of this age 
by the side of the small group of chromosomes a faint 
circular space is seen, resembling a degenerating nucleus. 
The chromosomes from the polar nucleus do not appear to 
persist for any length of time, for in eggs very little older 
they are already becoming scattered and difficult to count. 
The outer polar nucleus disappears as in N. ribesii, and the 
ego-nucleus sinks in and develops as in other cases. 
Of N. pavidus very few eggs were obtained, and all of 
these unfortunately represent stages later than the matura- 
tion divisions. Their ages are between two and five hours, 
