Sex Determination in Phylloxerans and Aphids 253 
This occurs at the first spermatocyte division. In the second 
spermatocyte division the larger cell containing six chromosomes 
divides, each chromosome dividing. Two spermatids result. 
nd e oe 
A B C D 
°° - ® 
2 & @ 
<—@ &< b* 
E F G ?. 
$e 0S, ote Oa 
I fF K L 
QR 
Fig. VIL Phylloxera caryecaulis. A, B, E-N, P, 8, equatorial plate of eggs of stem-mother; C, 
polar body of same egg; D, 0, Q, R, side views of polar spindle. 
The small cells, containing only four chromosomes, do not divide, 
and later degenerate. 
In the sexual female there is presumably a synapsis period, 
the twelve chromosomes pairing to give Six bivalents. “Two polar 
