Ox's THE EOEMATION OE THE EOG IN THE ANNULOSA. 
609 
it a cell, first, because I could not satisfy myself that it had a distinct membrane ; and 
secondly, because it is doubtful whether it is homologous with the true vitelligenous 
cells of insects, — these latter being coeval with the Purkinjean vesicle, while I never saw 
the vitelligenous vesicle of Artlironomalus except in eggs which were already of some 
size, and in which the yelk was beginning to become opake. We must, I think, 
seek for its analogue rather in the yelk-nucleus described first by Wittich in the eggs of 
spiders. 
GeopMlus* (Plate XVI. figs. 22-26). — In the form of the ovary and the first stages 
m the development of the eggs, this genus much resembles Artlironomalus. At the end 
of November, the long, narrow ovary contained a single series of about thirty or forty 
nearly mature eggs, which could even be perceived through the skin. Around them 
were others in earlier stages of development; but there was a considerable interval 
between the most advanced of these and the large ones, which latter were approximately 
equal in size, and are probably all laid together. 
In the young eggs the Purkinjean vesicle resembled that of Artlironomalus, and 
the macula was single, sometimes apparently homogeneous, sometimes nucleated, or, 
rather, perhaps vacuolated. In the smallest eggs the Purkinjean vesicle was round, 
but in others a little more advanced it exhibited one or two prolongations. What, 
however, struck me as very interesting was that the Purkinjean vesicles in several speci- 
mens, in which the eggs were rather larger, were no longer homogeneous, but appeared 
to consist of two substances, one surrounding the other (Plate XVI. figs. 22-26). The 
inner portion was generally produced at one or two places ; and as the boundary of the 
outer part was less affected or even quite circular, the inner part passed at these places 
almost or quite through the outer substance. In some cases the macula also appeared 
to have undergone subdivision. It appeared to me that portions of the Purkinjean 
vesicle in this manner gradually separated themselves from the rest. At any rate many 
of the eggs, at the stage when the yelk was beginning to become dark and granular, 
contained one, two, or thi’ee patches, which were apparently detached portions of the 
Purkinjean vesicle. 
I naturally refen’ed with much interest to the vitelline vesicle of Artlironomalus ; but 
in this genus the Purkinjean vesicle is always circular and homogeneous. If, therefore, 
the homogeneous yelk-masses of Geo]^hilus\ do originate in the manner indicated, it 
would appear that they are not homologous with the vitelline vesicle of Artlironomalus, 
which does not seem to be derived from the Purkinjean vesicle. It is, however, very 
improbable that two genera in other respects so nearly allied, should differ in a point 
* I examined G. acuminatiis, and also some specimens whicli had about fifty-three pairs of legs, filiform 
antennm, and the hasdar segment smaller than the sub-basilar. I am inclined to think from these characters 
that they must belong to G. Irevijpes, of which Newpoet had only seen a single specimen. 
t A somewhat similar though apparently more regular subdivision of the Purkinjean vesicle has been 
figured by Leitckaet (Enter, z. Nat. des Mens, und d. Thiere, 1858) as occurring in Aphis, Leuckaet 
also mentions a vitelline vesicle as existing in Geophilus ; but his species probably belonged to the nearly 
alhed genus Arthronomalus. 
