100 SEX INHERITANCE 
develop further. Since one maturation division of 
the chromosomes, presumably equational, takes 
place, the functional sperm has the haploid number 
of chromosomes. All the sperm are alike, and any 
egg that is fertilized gives rise to a female, which is 
diploid. 
In some of the aphids there may be a long suc- 
cession of parthenogenetic females, whose continu- 
OPE 
ORO 
Fig. 33B.—Spermatogenesis of the bear-berry aphid. a, }, c, first sper- 
matocyte division, with lagging chromosome. d, interkinesis stage. ¢,f, 9, 
second spermatocyte division of functional cell. 
ance has been shown to depend on environmental 
conditions. At the end of the series males and 
sexual females appear. 
The parthenogenetic females have the diploid 
number of chromosomes (Stevens, von Baer, 
