342 
ME. LUBBOCK ON THE OVA AND PSEITDOVA OF INSECTS. 
would be desirable to examine the formation of the ova in Coccus hesperidum^ an insect 
which, according to Dr. Letdig*, offers in this respect several very remarkable peculiarities. 
This investigation was completed, the drawings were all made, and the results written 
out almost exactly in their present form, by the beginning of June last, but I delayed 
the publication of them, in order to present at the same time some observations on the 
pseudova of Cynips and on the ovarian ova of the Insecta generally. 
In the mean time Professor Leuckaet published a paper on the same subject in 
Moleschott’s ‘ Untersuchungen zur Naturlehre des Menschen und der Thiere ’ for 
1858f, in which he anticipated the greater part of what I had to say about Coccus. It 
was, however, very satisfactory to me to find my observations confii’med by so eminent 
a naturalist, and the more so as in a great many points the descriptions and conclusions 
of Dr. Leydig seemed to me to be inaccurate. Although, therefore, most of the follow- 
ing description of the development of the pseudova of Coccus agrees with what has 
been published by Professor Leuckaet, yet when two such eminent anatomists came to 
very different conclusions, it seemed to me that the results obtained by a thir d observer 
were worthy of publication. 
It is well known that in Aphis the self-fertile individuals are viviparous, and the 
differences which have been pointed out by Professor Huxley, and more recently by 
Professor Leuckaet {1. c.), between the development of the ovarian product in the 
oviparous and viviparous forms, depend perhaps more on the difierent nature of the 
body that is to be produced than on the presence or absence of impregnation. According 
to Professors Huxley and Leuckaet, the vitelligenous cells are very distinct in the 
oviparous Aphis, while they are not developed or are inconspicuous in the viviparous 
form. The latter is, 1 believe, the true state of the case ; it is admitted that there are in 
the upper chamber of the egg-tube in the viviparous form, certain round cells, originally 
identical with the one which has developed itself into the germinal vesicle, and I con- 
sider these to represent the vitelligenous cells. 
In Coccus also we have one species, C. persicce, Avhich is truly oviparous, and in which 
the eggs when laid do not contain an embryo, while in Lecanium hespendum the pseudova 
are rapidly developed in the ovary, and when laid contain a fully-formed larva, which 
emerges from the egg-shell in a few hours. This latter species is therefore very nearly 
viviparous. Now it is remarkable, that whereas in the oviparous C. persicce the vitel- 
ligenous cells (Plate XVIII. figs. 11 & 12) are very conspicuous, in C. hespendum they are 
often with difficulty perceptible. Acetic acid generally renders their walls visible ; but 
if an ovary is examined in syrup, the majority of the egg-tubes show hardly a trace of 
the vitelligenous cells. In order, however, to compare the formation of the pseudova in 
Coccus and Cynips with that of the ova in insects generally, it is necessary to give an 
account of the latter, because up to the present time veiy little has been written on the 
subject, and that little is almost unknown in this country. Thanks, indeed, to the 
* ArcHv fiir Wissen. Zool. Bd. v. p. 1. 
t Zur Kenntnisa des G-enerationswecbsels und der Partbenogenesia bei den Insekten. 
