MATURATION OF UNFERTILISED EGG -IN TENTHREDINID, 581 
chromosomes, they may each divide so that double the number 
is found, but they do not appear to develop further. 
(7) In all the species the chromosome number is eight or 
nearly eight. This number is found at each end of both the 
first and second maturation spindles, and in the mitoses of 
the segmenting egg and in the blastoderm. No doubling of 
the chromosome number occurs during the early development 
of the egg, such as is described by Petrunkewitsch in the 
drone-egg, and itis concluded that at least in N. ribesii and 
P. luteolum no reduction division occurs, both the matura- 
tion divisions being equational. 
(8) Centrosomes are not visible in the maturation spindles 
but are found in the segmentation mitoses of both eggs from 
both virgin and impregnated females. 
The facts here described resemble, in many ways, those 
obtained by Petrunkewitsch in his work on the bee. The 
form of the maturation spindles, and the fusion of the second 
polar nucleus with the inner half of the first are closely simi- 
lar in the two cases, the chief difference being that in the bee 
the whole process takes place on the ventral side of the egg, 
in the sawflies on the dorsal. 
In the bee the “ copulation-nucleus”’ divides into a group 
of nuclei which aggregate protoplasm around themselves, and 
according to Petrunkewitsch ultimately give rise to the testes 
of the drone; and during all the earlier part of their develop- 
ment these cells are distinguished by having each a * double 
nucleus” (‘Doppelkern’). In the sawflies the conjugation of 
the polar nuclei takes place only in male-producing species, 
and the group of chromosomes which results ultimately disin- 
tegrates; but the fact that it commonly divides into two 
groups lying side by side may be compared with the produc- 
tion of “ double nuclei” in the bee. 
There are, however, several fundamental differences apart 
from the complete disintegration of the polar nuclei. In the 
bee a true reduction division is described as occurring, since 
sixteen chromosomes are figured in the equatorial plate of 
the first polar spindle, and only eight in the second polar 
voL. 49, pART 4,—NEW SERIES. 43 
