Sex Determination in Phylloxerans and Aphids 261 
rate (Fig. XTV, F). The other large chromosome shows no divi- 
sion at this time (Fig. XTV, F), nor does the smallest one, if it 
can be detected (Fig. XV, S). As the two pairs separate the 
es YW y 
Cs <z : ~f 
B 
lA Pa 
e Hw Me 
= BMH FR 
esa Sa 
} FOR on ee 
oh NW Ge op 
Fig. X1IIa Chromosomes of somatic cells of female embryos. 
larger chromosome becomes drawn out into a somewhat dumb- 
bell shaped mass (Fig. XTV, D). At this stage it is very noticeable 
