ere Experimental Zoology 
history, as shown by Blochmann, Dreyfus, and others. The 
young appear in the spring on the fir. They become mature 
and deposit eggs. The young developing from these eggs pro- 
duce galls, within which they mature as winged individuals. 
Most of these leave the fir and go to the larch, where each female 
deposits about 4o eggs, which, hatching in 10 to 14 days, pro- 
duce young that feed on the leaves. Later these wander to the 
stem, where they hide in the crevices throughout the winter. In 
the spring they grow larger and begin to lay eggs about the 
middle of April. The eggs soon hatch and the young wander up- 
ward to the young needles, on which they feed and grow to winged 
parthenogenetic females. These leave the larch about the end 
of May and fly to the fir, settling down on the under sides of 
the old leaves, where they deposit 8 to 10 stalked eggs from which 
sexual males and females develop. These pair and the female 
lays one egg on the stem. The eggs develop slowly, the young 
emerging in October. They wander to the bases of the buds, 
stick the proboscis into them, and winter in this condition. In 
the spring the female deposits many eggs, from which the young 
that emerge are those that produce the galls first mentioned. 
This brings the cycle back to the starting point. 
There is also in Chermes what is known as a parallel or col- 
lateral series. Part of the parthenogenetic females on the fir 
that are late in leaving the galls remain on the fir, and deposit their 
eggs there (instead of on the larch). The young wander to the 
ends of the branches, where they remain until the next spring with 
the proboscis stuck into the tissues of the buds. In the spring 
they produce galls. Presumably the cycle may begin again from 
the individuals that emerge from these galls, which have, as it 
were, short-circuited the life-cycle. 
It is of great interest to observe that the sexual forms do not 
appear in this short-circuited generation that remains on the fir, 
and the inference is plausible that the conditions existing on the 
larch are those that call forth the sexual forms. 
In another species, the phylloxera of the grape, the alterna- 
tion of generations takes place between the roots and the leaves. 
