6 
A. D. Darbishire. 
spermatogenesis, however, results in the formation of dimorphic 
sperms, half of which carry three chromosomes, and the rest two 
(see Fig. 5). 
Now it will be remembered that fertilisation gives only females; 
this result, as Morgan and v. Baehr showed, is brought about by 
the degeneration of all the two-chromosome sperms. Fertilisation 
therefore is always effected by the union of three-chromosome 
sperms and ova, resulting in a six-chromosome zygote, which is 
potentially female. 
The anomaly of the production of females only, from fertilised 
ova, is therefore satisfactorily explained, and brought into line with 
the phenomena in dioecious forms, by the discovery of the 
degeneration of the two-chromosome sperms, which are potentially 
male-producing. Thus the apparently homozygous male seems to 
be really heterozygous, but with its heterozygousness in a state of 
degeneration. The anomaly of the production of males and females 
by the supposed homozygous female is probably a real difficulty, 
but it will be best discussed after describing the cytological 
phenomena presented by the hornet and the bee. 
The males of the bee and hornet develop from ova which have 
undergone reduction in maturation ; hence follows the startling 
fact that all the cells of the male possess only the haploid number 
of chromosomes. Consequently the sperm-mother-cells of the bee 
or hornet have half the number of somatic chromosomes found in 
the female, and hence there is no need for a reducing division in 
spermatogenesis. In the latter process, however, the heterotype 
division does occur, but no nuclear matter passes into one of the 
products of division ; and only one of the two potential spermatozoa, 
into which the other product divides, becomes, in the bee, a 
functional sperm, although both are functional in the hornet. 
Thus all the sperms retain the haploid number of chromosomes. 
These sperms, on fertilising eggs similar to those from which their 
producer arose, develop into females. The cytological details, 
however, have not been fully worked out, so that an interpretation 
of the bare facts is difficult, and is probably best postponed until 
more facts are known. The degeneration of three-quarters of the 
the sperms, however, leads us to infer, from the analogy of Aphids 
and Phylloxera , that the male bee or hornet is also a degenerate 
heterozygote. 
The production of males and females by the female Bee, 
Hornet, Aphids or Phylloxera, however, cannot be explained on the 
