596 
MR. LUBBOCK ON THE OENEEATIVE OEG-ANS, ANT) 
ovary as in Coccus, &c. ; but, on the other hand, the Purkinjean vesicle lies on the outer 
side of the epithelial layer {d), as in Glomeris, and in consequence the egg-follicle, 
which in Coccus consists of both the ovarian membranes (so far as the epithelial layer 
can be called a membrane), and in Glomeris of the epithelial layer only, is in the Pha- 
langidce, and perhaps all the Arachnida, formed only by the outer membrane. Con- 
sequently, while in the insects the mature ovum passes into the ovary through the neck 
of the follicle, in Myriapods and the Arachnida it bursts through the epithelial layer, 
in the former at its free, and in the latter at its attached end. 
If these characteristics are found eventually to hold good throughout the Myriapods 
and Arachnida, the differences thus shown to exist between these groups will be of great 
interest; but it is too early to generalize on the subject with much confidence. More- 
over, it often happens that one or a few epithelial cells are attached in Arachnida to 
the inner side of the follicle-wall. This happens, however (so far as my observations 
go), without any regularity, and the cells thus present fulfil perhaps no important 
function in the formation of the egg. The Crustacea* appear to differ from the three 
preceding groups in the fact that their eggs do not possess separate follicles. The 
nuclei of the epithelial cells in the ovary of Oniscus are about sifp o ths of an inch in 
diameter, with a bright nucleolus ; but along the inner edge of the ovary one or two may 
generally be found as much as ^^oths of an inch in diameter, but not otherwise differ- 
ing from the small ones. Between these extremes all intermediate stages may with 
patience be discovered. 
When the epithelial nucleus has attained the above size, or even a little earlier, a 
deposit of dark, structureless matter appears round it. This is the commencement of 
the yelk, and has at first no bounding membrane, as the membrane of the cell itself 
seems to perish at a very early stage. It soon, however, acquires a clearly marked 
outline, though it is not until it is full-grown that any true membrane is formed 
rormd it. The outline is, however, so clear and sharp that it is often difficult to beheve 
that there is in reality no membrane. Pressure, however, clearly shows that there is 
none. 
In lAgia oceanica the process is almost exactly similar ; and although the animal is so 
much larger, the epithelial cells, their nuclei, and the young Purkinjean vesicles are as 
nearly as possible of the same size as in Oniscus. 
* To M. ScHoBi (Zeitschrift fiir "Wiss. Zool. 1860, p. 465) is, I believe, due the credit of being the first to 
describe the position of the female orifice and the presence of a spermatheca in the Oniscidse. I had my- 
self independently made the same observations in Oniscus as he has in his new genus Saploplithahnus, and 
can therefore confirm what he says on the subject, though the size of the eggs is so great, compared ^vith 
that of the orifice, that I am still at a loss to understand how they make their exit. M. Schobl found the 
spermatheca full of spermatozoa in May only, but in Oniscus I found them in January, February, Jime, 
and August, the only months in which I looked for them. They were always motionless, and I never found 
in the female any of the large round cellular bodies which occur in the generative organs of the male. The 
spermatozoa were not confined to the spermatheca, but I met with them also in the oviduct, and even 
frequently (if not always) in the ovary itself. 
