DEVELOPMENT OF CYNIPID HYPERPARASITES 459 
in the same manner throughout the group. Silvestri (28, 
p- 67) has described its formation in Encyrtus aphidi- 
vorus, Mayr., where it originates as a delamination of the 
peripheral cells of the blastula. In the same work he gives an 
account of its origin in Oophthora semblidis, where at 
a certain point, the central protoplasm of the blastocoele 
breaks out through the blastoderm, bearing with it some free 
nuclei from the interior. This extruded protoplasm extends 
round the egg and forms the membrane. 
In 1917 Gatenby (6) eriticized the conclusions of Silvestri 
with regard to the latter species. Working on the development 
TEXT-FIG. 3. 
Larva of Aphidius containing two embryos of Charips. x70. 
of Trichogramma evanescens, a form which he later 
recognized as con-generic with Oophthora, Gatenby showed 
that during the formation of the blastula small masses of 
nuclear matter are extruded into the blastocoele. Later, 
these, with the surrounding cytoplasm, move towards the 
periphery and ultimately stream out through the blastoderm. 
If the chorion is ruptured, the mass floats out into the host 
and soon perishes. If the chorion remains intact the extruded 
mass is flattened and extended by its pressure, until it surrounds 
the embryo, and the nuclei which it contains give it a fictitious 
cellular appearance. 
Owing to the limited material at my disposal I originally 
intended to make no reference to the embryology of Charips ; 
