48 ON THE AGAMIC REPRODUCTION AND MORPHOLOGY OF APHIS 
of the blastoderm of a more pellucid aspect than the rest, and 
separated from it by a more or less distinct line of demarcation. 
This layer (g) could be detected only on the dorsal face of the 
thoracic and cephalic segments, and owed its superior transparency 
to the comparatively large size of the clear cavities surrounding its 
endoplasts. 
That portion of the layer which covered the posterior portion of 
the thoracic segment was particularly remarkable for the size and 
clearness of its cells and their endoplasts (7). In the progress of 
development, the central portion of the alimentary canal occupies a 
place nearly corresponding to the centre of the clear layer; while, if 
we trace out the site of the rest of the mass in larger and Jarger 
embryos (Pl. XNNVIII. [Plate 3] figs. 1, 3, 4, 5), we find it always 
retaining the same relative position to the reflected abdominal hood, 
but gradually enlarging, and eventually becoming subdivided into. 
five oval lobes upon each side, each of which surrounds itself with a 
membrane, and assumes the form of the terminal chamber of one of 
the pseudovarial cca. It would be a great mistake to suppose that 
it is only one of these chambers, however ; it is in fact the rudiment 
of an entire cecum; and before the embryo leaves the parent, it 
becomes divided into three chambers by the gradual development 
and metamorphosis of pseudova in the way described above. 
The granular pseudovitellus takes no part whatever in the forma- 
tion of the reproductive organs. In embryos of j,th of an inch in 
length, I could very plainly observe a clear space with an endoplast 
in the middle of each of its spheroidal masses (Pl. XNAVIIL. 
[Plate 3] fig. 3). Similar masses constitute a larger or smaller 
proportion of the corpus adiposum of the larva and adult insect ;, 
and I believe that the latter proceeds from the former. 
S85. Summary and Comparison of Germs and Ova 
I will now sum up the results of the observations which have 
been detailed in the preceding pages. 
1. The pseudovarium consists of vagina, oviducts, and pseudo- 
Varian czeca, 
2. The vagina is unprovided with either spermatheca or colleterial 
vlands. 
3. The pseudovarian caca are each divided into many chambers 
by constrictions. 
4. The apical chamber contains bodies which are not distinguishable 
from the germinal vesicles and spots of the true ovaria. 
5. These bodies, surrounded by a mass of clear substance repre- 
