208 PROF. HUXLEY ON THE AGAMIC REPRODUCTION 
the oviduet; but as development proceeds, the upper globular chamber becomes by 
degrees separated by a constriction, and at the same time a great difference makes its 
appearance between the upper and the lower chambers : for the lower chamber contains 
a finely granular mass which gradually becomes modelled into an oval egg; the upper 
chamber, on the other hand, is filled with vesicular bodies, in which smaller vesicles con- 
taining a nucleus are distinguishable. If these bodies are to be regarded as germs of 
ova (Wollte man diese blasenfórmigen Körper als Eier-keime betrachten), we may assume 
that these Aphides were capable of bringing forth more than eight ova.” 
Von Siebold then goes on to describe the colleterial glands, and the spermatheca, which 
had not before been seen. If the ovaries of Aphis Loniceræ are not constructed on a totally 
different plan from those of the species I have described, it is, I think, pretty clear that 
Von Siebold, like Morren, has mistaken the ovarian glands for the rudiments of the ova. 
. Indeed, his phraseology indicates that he himself had no great confidence in his interpre- 
tation of the parts. 
$ 4. The Development of the Pseudovarium. 
In the viviparous female, the germ increases in size, and gradually becomes separated 
from the terminal chamber by the successive development and separation by constriction 
of new pseudova. The number of chambers between the terminal one and that nearest 
the vagina, therefore, varies until it attains its maximum, which is necessarily regulated 
by the ratio between the time required for the perfection and birth of a larva, and the rate 
at which new pseudova are detached from the pseudovarium. In the species of Aphis 
which I examined, I found ordinarily four or five such chambers. Germs between zooth 
and 55th of an inch in length presented the following characters (Pl. XX XVII. fig. 1 :— 
They exhibit a central darkish matter, surrounded by a clear cortex. The latter is com- 
posed of a single layer of a substance similar in appearance to that composing the mass of 
the germ above described, while the central substance is obscured by a number of minute 
granules which hide its internal structure. N evertheless, I have occasionally detected 
what I believe to be endoplasts, scattered through its substance, as in Pl. XXXVII. fig. 1, 
which represents a germ in this stage treated with very dilute acetic acid; and as in a 
more advanced condition we shall find such bodies easily recognizable, I do not doubt 
that the central substance has the same fundamental composition as the peripheral layer. 
The central mass, it will be observed, completely simulates the vitellus- of an impregnated 
ovum; and I will therefore term it a « pseudovitellus.” The peripheral clear layer i$ 
on the other hand, in all essential respects comparable to a blastodermic vesicle ; and I see 
no reason why it should not be called a blastoderm, since the term is not necessarily con- 
fined to the product of impregnation. 
Ina more advanced condition (fig. 8), the blastoderm has become thicker in all parts, 80 
as to consist of at least two or three layers of “cells;” but the thickening shows itself 
ev ae ee side of the distal end of the germ (that turned towards the vagina), 
Scale in ina m. ri twice as thick as in other parts. A linear bui 
ET URN p x thickened layer (fig. 4); and at the same time indibi 
"ui en ie etween the distal extremity of the thickened portion and 
: | rm: it is as if the latter were giving way at this point. In some 
