962 
Journal of Agricultural Research 
Vol. V, No. 21 
Development is resumed in the late winter or early spring (March 12 to 
15, during 1914 and 1915, at Vienna, Va.). Growth is not resumed uni¬ 
formly, even in a group of eggs on a single twig, some starting two or three 
days before the majority and a few not beginning to grow till nearly the 
end of March. This renewed development is accompanied by a move¬ 
ment of the embryo through the yolk toward the posterior pole till tha t 
portion of the amnion which lies above the head comes in contact with the 
serosa at its junction with the polar organ. The two envelopes then 
rupture at this point and the embryo revolves about its transverse axis 
to its definitive position. 
From this time on development is rapid. The serosa contracts, and is 
invaginated and absorbed. The appendages are completed, the devel¬ 
opment of the digestive tract is consummated; nervous and muscular 
systems are perfected. Within a period of from five days to two weeks, 
depending apparently entirely upon temperature conditions, the insect 
is ready to hatch. 
Ovarian yolk. —At the posterior pole of the egg there is situated 
an almost spherical, dark-staining body. This has been termed the 
secondary yolk by most writers, but has been designated the “ ovarian 
yolk” by Webster and Phillips (17, p. 95). The writers are unable to 
follow the formation of this body, as no egg material earlier than those 
eggs deposited by the female was preserved. Tannreuther (13) studied 
its formation in Melanomntherium salicis L. He states that it is formed 
from the follicular nuclei of the oviduct wall, these dividing to form small 
vesicles which later unite and form common spherical masses. In the 
writer’s earliest fertilized material (fertilized less than 24 hours) the 
ovarian yolk consists of a densely granular, almost spherical mnw con¬ 
taining a number of large cells (PI. LXVIII, fig. 7) which would corre¬ 
spond fairly well to the figures given by Tannreuther. At this rimo 
(PI. LXVIII, fig. 1) the writers are unable to observe any cleavage cells 
within the body of the yolk, although there are at the anterior pole a 
number of dark-staining bodies well separated, but fo rming a dome¬ 
shaped structure conforming to the shape of the anterior part of the egg. 
One thing is worthy of note in this connection. In unfertilized eggs, 
ranging in age from a few hours to 11 days, the ovarian yolk is a uniform, 
finely granular mass (PI. LXVIII, fig. 3) without any of the large cells 
met with even in our earliest fertilized material. This leads to the belief 
that these bodies are associated with and appear only in connection with 
the beginning of growth. At the time the blastoderm is completely 
formed these bodies are present within the ovarian yolk and are sur¬ 
rounded by darker staining areas (PI. LXVIII, fig. 2.) When the 
blastoderm is completely formed it covers the entire surface of the egg 
with the exception of the ovarian yolk, and invagination takes place 
about this yolk. (A single yolk cell is shown in Plate LXVIII, figure 6.) 
