22 Mr Doncaster, On the Maturation of the Germ-Cells 
On the Maturation of the Germ-Cells in the Saivfly, Nematus 
ribesii (Third Note*), by L. Doncaster, M.A., King’s College. 
[ Received 20 November, 1906.] 
In two previous notes to the Cambridge Philosophical Society 
(Proc. Vol. xii. p. 474 and xm. p. 103), and in a fuller paper 
(Q.J. M. S. Vol. xlix. p. 561), I have described the maturation of 
the egg in Nematus ribesii. Since in all mitoses, whether of the 
polar divisions or in the developing egg, 8 chromosomes were 
found, it was concluded that no reduction took place, and that 
both the polar mitoses were equational. At the time those papers 
were written I had not completed the study of the fertilized egg, 
so that no suggestion could be offered to explain the difficulty of 
how normal fertilization could take place if there is no reduction 
of chromosomes. For many months I was quite unable to follow 
the entrance of the spermatozoon into the egg and its conversion 
into the male pronucleus, and I have still failed to find the earlier 
stages, but after cutting some hundreds of eggs laid by impreg- 
nated females I succeeded in observing the conjugation of male 
and female pronuclei. When it had been shown that true fertili- 
zation (“ syngamy ”) does take place, it was necessary to re-examine 
the maturation divisions, in order to explain the discrepancy 
between the existence of conjugation of male and female pronuclei 
and the absence of reducing divisions in the maturation of the 
egg- . 
Since the technical difficulties in investigating the early stages 
of the egg are considerable, I determined to work first at the 
maturation of the spermatozoa. In the spermatogonia the nucleus 
is large with about 8 chromatin masses and usually one or more 
plasmosomes. In mitoses 8 chromosomes are visible. In the 
prophase of the first spermatocyte division there are sometimes 8, 
but more often 4 chromatin masses ; in the latter case each is 
generally more or less distinctly double or quadruple, suggesting 
that the primary 8 chromosomes have paired to form 4 “ gemini.” 
In the equatorial plate of the first division there are 4 chromo- 
somes packed close together, and they seem to divide in the 
heterotype manner sending 4 to each pole. In the second division 
there are again 4, which divide so that 4 go into each spermatid. 
It appears therefore that in the spermatogenesis normal reduction 
takes place, the somatic number 8 being reduced to 4. 
A full paper with figures is being published elsewhere. 
