MATURATION OF UNFERTILISED EGG IN TENTHREDINIDE. 569 
two groups, those of one group may each divide into two, and 
either remain associated together or, in some cases, separate 
into two sets, so that altogether three groups are found lying 
side by side. There is no regularity, however, in these 
processes ; the chromosomes in the polar protoplasm some- 
times remain as a compact group, in others become scattered ; 
their number varies in different eggs, but otherwise they 
remain unaltered until the nuclei derived from the egg- 
nucleus begins to come to the surface to form the blastoderm. 
Beyond this stage I have been unable to trace them. 
Although nearly all the eggs examined follow the course 
here described, it should be mentioned that in two cases at 
least abnormalities have been found. In one of these, an egg 
preserved six hours after it was laid, in addition to a group 
of chromosomes in the “ polar protoplasm,” there is, nearer 
the edge of the egg, and slightly more anteriorly, an oval 
reticular nucleus with well-marked membrane. It is possible 
that this is the outer half of the first polar nucleus, which 
usually disappears several hours earlier, but in another egg, 
the exact age of which is, unfortunately, unknown, though 
probably between four and five hours, two such nuclei appear. 
One of these is close to the edge of the egg, and the other 
slightly deeper, i.e. in just the positions of the two halves of 
the first polar nucleus at an earlier stage; the chromosomes 
derived from the “ copulation-nucleus” lie grouped in several 
irregular masses in the “polar protoplasm” near the two 
nuclei described, and the yolk contains a number of scattered 
nuclei, doubtless derived from the egg-nucleus in the ordinary 
way (Pl. 35, fig. 12). 
It will be seen below that the arrangement here described 
as abnormal is exactly that commonly found in the species 
which yield females from virgin eggs, and it is known that 
something under 1 per cent. of females may be reared from 
virgin eggs of N. ribesii. 
By the time the two inner polar nuclei have coalesced the 
outermost has usually quite disappeared, but in this respect 
different eggs vary somewhat, and in a few cases traces of it 
