ME. LUBBOCK ON THE OVA AND PSEUDOVA OF INSECTS. 
361 
bably failed to perceive the germinal vesicle, because he generally examined his speci- 
mens in a vreak solution of acetic acid, -which causes it to swell and then disappear in a 
few moments. 
At about the same time as the germinal vesicle, the oil-globules make their appear- 
ance, and soon become the most conspicuous part of the egg. They are at first very 
minute, but in a mature egg the larger ones are as much as -0016 in diameter, from 
which to a mere granule every intermediate stage may be found. These globules are 
of a yellowish colour, and refract light, like the oil-globules in milk. They are also 
affected in a similar manner by acetic acid and sulphuric ether, being dissolved and 
running into one another if subjected to the latter ; while in the former they split at 
the edges, as in Plate XVI. fig. 7, and finally become marked by irregular fine lines, 
some of which also seem to project from the side. Neither oxalic nor tartaric acid have 
much effect on the oil-globules. 
The epithelial cells contain almost always several yellowish-green minute globules, 
which appear to me to agree in every respect, except in size, with the oil-globules ; and 
it seems to me probable therefore that these are partly secreted by that side of the 
epithelial cells which is turned towards the inside of the egg-follicle. 
It is e-vidently very difficult to obtain any decisive proof upon this point, and it might 
rather perhaps be concluded, from the descriptions and figures of M. de Quateepages*, 
that the oil-globules are secreted by the germinal vesicle. I have, however, never found that 
they are particularly collected round the germinal vesicle, which, moreover, is sometimes 
apparently absent after the formation of oil-globules has commenced (Plate XVIII. fig. 3). 
The oil-globules may often be seen lying somewhat compressed together (so as to have 
one or more straight sides), without running together, which indicates, I think, that the 
outer surface is covered by a somewhat harder pellicle or skin, though the effect of 
sulphuric ether shows, if any proof was wanting, that they are not covered by any 
distinct membrane. 
Very soon after the appearance of the first oil-globules, the basal part of the egg- 
follicle begins to swell up, and to be separated from the upper part by a gradually 
deepening constriction, so that the egg-follicle comes, as described by MM. Leydig and 
Leuckaet, to consist of two chambers, the upper one of which is spherical, and the 
lower fusiform. The upper chamber, though short, is at first much broader than the 
loAver, and contains the three vitelligenous cells (e); the lower chamber contains the 
oil-globules, and the germinal vesicle is situated at the apical end of the lower chamber. 
Besides the oil-globules, the lower chamber contains also some few small yelk-cells 
and immense numbers of very small greenish granules, resembling in many respects very 
minute oil-globules ; and I am not, as already stated, inclined to believe that these latter 
are produced by the coalescence of the minute green globules. 
The egg-follicle continues to grow, and the germinal vesicle remains visible for some 
time, the largest specimen in which I have seen it being Plate XVIII. fig. 5. 
* Ann. des Sci. Nat. 1849, p. 202. 
