ox THE EOEMATIOX OF THE EGG IN THE AXXTJLOSA. 
623 
In describing the so-caUed “winter-ova” of Lacimilaria socialis, Professor Huxley 
says “ It will be observed that all these authors consider the winter-ova, or ephippial 
ova, and the ordinary ova to be essentially identical, only that the former have an outer 
case. The truth is that they are essentially different structures. The true ova are 
single cells which have undergone a special development. The ephippial ova are aggre- 
gations of cells (in fact, larger or smaller portions, sometimes the whole of the ovary) 
which become enveloped in a shell, and simulate true ova.” This aggregation of several 
cells (one of them putting on the appearance and fulfilling the functions of a Purkin- 
jean vesicle, and the whole becoming enveloped in a shell) is, however, the ordinary and 
only method of egg-development in many animals. In the Trematode and Cestoid 
worms, and the gi’eater number of the Titrlellaria^ the yelk and the Purkinjean vesicle 
are formed in two separate organs. In Piscicola, according to Leydig, the mature egg 
contains, besides the Purkinjean vesicle and the ordinary yelk, a number of nucleated 
cells f. 
In the Mites and Spiders, in Chelifer, OMsium, the Phalangidm, and, so far as I know, 
all the Arachnida, the egg is the product of a single cell. 
On the other hand, we find that complex eggs alone are present in vast numbers of 
insects, namely, in all the Lepidoptera, Diptera, Neuroptera (excluding the Libellulidee 
and allied genera), Hymenoptera, Hemiptera, Homoptera, and Coleoptera. We are as 
yet ignorant of the mode of egg-development in the Thripsidse and the Strepsiptera ; nor 
does it seem quite clear whether the development of the pseudovum in A])Jiis can 
be referred to the complex type. It would appear, however, from the statements of 
Huxley, Leydig, and Leuckart, that in the opinion of these three eminent naturalists 
the pseudo\’um is a derivative of a single ovarian cell, and differs therefore in this 
respect from the ovum of the impregnated female. 
We know little as yet about the early stages of egg- formation in the Crustacea ; but 
it vrould appear that the simple mode prevails generally throughout this class, with the 
exception of the Daphnidce. 
As regards the Eotatoria, the so-called wunter-eggs have been observed in Hydatina, 
Bracliionus, and Notommata, as well as in Lacinularia •, and we may probably conclude 
that in these and other allied genera the development of these eggs is on the same type, 
while “ summer-eggs,” again, are formed from one cell. 
Among the Myriapoda the eggs of Litliohius^ Crypto])S, Geo^hilus, Arthronomalus, 
Polydesnms, and lulus are probably simple. At least I am disposed to think that the 
vitelline vesicle is homologous wdth the yelk-nucleus of spiders; but I have not yet 
been able to ascertain this point satisfactorily. 
Glomeris, how'ever, offers apparently an exception to the rule so general among the 
Myriapods, as the large rounded bodies present in the egg-capsule (Plate XVI. figs. I, 2) 
are probably homologous with the vitelligenous cells of insects. 
* Microscopical Journal, vol. i. p. 14. 
t Zeit. f. tViss. Zool. 1849, pt. 1. pi. 10. fig. 56. 
