582 L. DONCASTER. 
mitoses. In the sawflies the number in all the divisions is 
constant, and no trace was seen of tetrads or dyads to indi- 
cate the occurrence of reduction. In the parthenogenetic 
ego of the bee the somatic number of chromosomes is said to 
be restored by a process of doubling, which occurs before the 
first division of the egg-nucleus, and which does not take 
place if the egg is fertilised. In the sawflies no such doubling 
takes place, and the somatic number is the same, at least up 
to the formation of the blastoderm, as the number in the 
polar mitoses. 
Among the most important papers on the maturation of 
the insect-egg are those of Henking (5, 6), and many points 
of interest arise from a comparison of my work with his. The 
Hymenoptera investigated by Henking were Rhodites rosx 
and Lasius niger, the first of which is parthenogenetic and 
produced chiefly females from virgin eggs. The early de- 
velopment of the polar nuclei in this species and in fertilised 
egos of L. niger is closely similar to that found by 
Petrunkewitsch in the bee; the three polar nuclei consist of 
groups of chromosomes, and the two inner groups move to- 
gether until they lie side by side in a clear space near the 
edge of the egg. Their development was not traced further. 
In virgin eggs of L. niger this course was sometimes followed, 
but in others no attraction between the chromosome groups 
took place, and in a third lot all three groups joined together. 
A fusion of all three polar nuclei also occurred in fertilised 
egos of Pieris brassice and Musca vomitoria, in both 
of which species all the polar nuclei were vesicular. 
Fusion of the two inner nuclei, or at least a convergence 
resulting in a group of chrososomes lying close together, 
took place also in some beetles, viz. in some eggs (but not 
all) of Agelastica alni, and in Adimonia tanaceti 
and Crioceris asparagi. In other beetles, e.g. Donacia 
sp.. Lampyris splendidula, no fusion of nuclei took place, 
and in L. splendidula and Pyrrhocoris apterus both 
polar bodies are extruded from the egg and the first does 
not divide. Division of the first polar nucleus without subse- 
