1917-18.] Germ-Banc! in the Egg of the Holly Tortrix Moth. 155 
likens the ventral plate to a watch-glass in shape. Of these, Bobretzky’s 
figure most nearly resembles the germ rudiment of Eudemis. 
Owing to the formation of the amnion, the ventral plate becomes 
detached from the surface of the egg, sinks into the yolk, begins to elongate 
in the direction of the long axis of the egg, at the same time shrinking in 
width, and gradually assumes a C-shape — the germ-band. Almost all the 
researches on the embryology of the Lepidoptera have commenced with the 
formed germ-band, or have been carried out on later phases. 
Observations on Eudemis njevana. 
External Aspect of the Egg. 
The female moth of Eudemis ncevana deposits her eggs in August, 
one by one, on the under sides of holly leaves, fastening them by means of 
a sticky secretion. The egg is scale-like, oval, scarcely 1 mm. in length, 
about *7 mm. in breadth, and T2 mm. in thickness at the thickest part.* 
It adheres to the leaf by the ventral surface, which is flat, the free (dorsal) 
surface being convex, the convexity increasing with the development of 
the embryo. Investing the egg is a double envelope, the inner pellicle — 
the vitelline membrane, — perfectly transparent and very thin; the other 
— the chorion, — tougher, and bearing an indistinct honeycomb sculptur- 
ing.]- Near the cephalic end are three or four minute micropyles closely 
grouped. When freshly laid the greenish contents completely fill the egg, 
but by about the seventh day after oviposition the appearance of the egg 
has greatly changed, the contents having gradually contracted, so that, 
viewed from the surface, there is a broad, empty peripheral part round the 
central mass, which appears now to be yellow or orange-coloured owing to 
the tint of the cuticle-like secretion of the serosa which has formed over it. 
Methods. 
I obtained eggs for experimental purposes by collecting more than 100 
chrysalids and breeding out the moths in a large breeding-cage. The eggs 
are deposited in the twilight. By means of branchlets of holly supplied 
to the moths every afternoon, and removed after dusk, I was able to get 
eggs in any required stage of development. 
* There is, however, considerable variation in the dimensions. 
+ Tichomiroff studied the chemical nature of the chorion of Bombyx mori , and found that 
it differs in composition from both chitin and horn. This peculiar substance he calls 
“ chorionin.” Following up his investigations, Lecaillon and Henneguy, working on the eggs 
of several other insects, arrived at similar results. 
