104 L. DONCASTEH. 



time^ but in fertilised eggs they frequently divide compara- 

 tively early, giving groups containing as many as sixteen 

 chromosomes rather irregularly arranged in the " polar 

 protoplasm." That this difference in behaviour is really 

 connected with fertilisation is made probable by the fact 

 that it rarely, if ever, occurs in eggs which are certainly 

 virgin, but in the eggs laid by impregnated females it is 

 frequent. Further, in several eggs laid by impregnated 

 females the polar nuclei follow the typical virgin arrange- 

 ment, and in these the little rayed protoplasm masses in the 

 yolk, characteristic of fertilised eggs, are absent; but 

 other eggs laid by the same female have the fertilised type 

 of polar chromosomes, and in these the rayed protoplasm 

 patches are also present. 



It appears, therefore, that the fertilisation of the egg 

 nucleus, or the presence of spermatozoa in the egg, in some 

 way influences the behaviour of the polar nuclei. 



Spermatogenesis. 



When it had been shown that normal fertilization could 

 take place in N. ribesii, it became necessary to re-examine 

 the maturation divisions in order to make certain about the 

 chromosome number, which I asserted in the previous paper 

 to be eight both in the maturation and in the somatic 

 mitoses, and also apparently in fertilized eggs. The matura- 

 tion of the egg begins immediately after it is laid, so that it 

 is very difficult to get good preparations of the early stages, 

 and I therefore decided to examine the matter first in the 

 development of the spermatozoa. 



In very young male pupae, shortly after the larval skin is 

 cast in the cocoon, the testes consist of compact groups of 

 cells at the sides of the alimentary canal. These cells 

 (spermatogonia) have relatively large nuclei containing a 

 conspicuous nucleolus fplasmosome) and eight or about eight 

 chromatin masses apparently attached to the nuclear mem- 

 brane (fig. 5). Division figures are scarce, but when found 



