Sex Determination in Phylloxerans and Aphids 295 
genesis another year. It is not inconceivable that they produce a 
different gall another year, but as yet there are no facts to support 
this view. 
The sexual males and females of P. fallax are shown in Plate I, 
Figs, 1-4, the first two drawn from life, the second two from pre- 
served specimens. The male shown in Fig. 1 was probably 
slightly flattened, while held under the cover slip, so that the pre- 
served specimen, Fig. 3, gives a truer idea of the form. 
The sexual male and female of P. caryzcaulis are shown in Figs. 
5and6. The difference in size is less marked than in the last case. 
The remaining three figures 7, 8, 9, of the Plate, represent the 
single type of individual that emerges from the eggs of the winged 
migrant of three species. ‘The first of these comes from a large, 
elongated stem-gall, quite abundant in Woods Hole. ‘The gall, 
closed at first, cracks open to set free its migrants from whose 
eggs this form hatches. The species appears to be P. subel- 
liptica, Shriner; but Shriner’s description is very incomplete. 
Pergande who has seen only the gall questions whether it may not 
be a form of P. caryzcaulis. [had in fact at first confused these 
two at Woods Hole, but an examination of P. caryzcaulis from 
Woods Hole showed migrants with two kinds of eggs as in the 
New Bedford type, while the migrants of the present gall contain 
only one kind of egg. Obviously they are different species, or else 
different phases of the same cycle. The form shown in Fig. 7 
is entirely different from the sexual forms of P. caryecaulis. It is 
not uninteresting to find that the polar plates of the eggs of the 
migrants of this form show six chromosomes, (Figs. XIX, 4-F) 
as in P. carvecaulis, but these are not of different sizes. 
In Plate I, Fig. 8, is shown the individual that emerges fromthe 
egg of the migrant of a species which [ provisionally identify as 
P. caryeglobuli, Walsh. Pergande cites the descriptions of Walsh 
and of Shriner, but questions whether Shriner’s account does not 
apply to another species. Walsh’s description is too brief for 
accurate identification. ‘The sexual (?) form here described is so 
specifically marked that in future there should be no difficulty in 
settling the status of this species, if the plan of hatching the eggs 
of the winged migrant, here proposed, is followed. 
