Sex Determination in Phylloxerans and Aphids 259 
not six as stated, although in the embryos from female eggs the 
number of chromosomes counted is six (Figs. XIII and XIII, 4). 
The spermatogonia of P. caryzcaulis also show either five nearly 
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Fig. XII’ Chromosomes of somatic cells of male embryos; six chromosome type. 
equal chromosomes, or five such and one very small one. The 
spermatocytes show an equatorial plate made up of three equal 
or nearly equal-sized chromosomes (Fig. XIV, C), or else of three 
