622 
m. LUBBOCK ON THE GENEEATIVE OEGANS, AND 
regards their origin and mode of development, the eggs of some {Argulus, lAmulus, See.) 
are homologous with the Pnrkinjean vesicles of others (Oniscus, Ascaris, Sec.). 
It is easy to convince oneself that the egg cannot be considered as a modified ovarian 
cell, at any rate in certain cases; and a single inspection of a female Glomeris, for 
instance, will leave no doubt upon this point. On the other hand, I was myself at first 
inclined to believe that the second process did occur in some animals. Thus in 
PoJydesmus complmatus it seems at first sight evident that each of the minutest eggs 
is constituted by a cell whose nucleus forms the Purkinjean vesicle, and whose cell- 
wall gradually becomes the vitelline membrane. The same appearance is also repre- 
sented by the young eggs of Cryptops, Artlwonomaliis., GeoyAiilus, &c., and is sometimes 
seen also in those of lulus ; but in this latter genus it is easy to see, especially if pure 
water is used, that many, if not all, of the young eggs have in reality no vitelline mem- 
brane. In all the Chilopods I have, however, found scarcely a case in which the Pur- 
kinjean vesicle is not already surrounded by a spherical mass of clear yelk with a per- 
fectly distinct border ; in a few cases, indeed, I believe myself to have done so, and in 
others, in which a membrane is apparently present, it is easy to convince oneself that 
tills is an illusion, since if a portion is cut off, the new surface equally appears to 
possess a distinct membrane. 
On the whole, therefore, it seems probable that in Argulus., &c., the youngest 
eggs yet observed may not have represented the earliest stage, but may have at an 
earlier period consisted only of the Purkinjean vesicle, and that the sharp edge of the 
yelk may have had the appearance of a true membrane. That no free Purkinjean 
vesicles were found with those which were already surrounded by yelk, may perhaps 
have depended on the state of the animals when they were discovered. Neither 
"STaG-VEE nor Stein found in the Neuroptera, Orthoptera, and Lepidoptera any Pur- 
kinjean vesicles which were not already surrounded by yelk; but Professor H. Meyee, 
who examined certain Lepidoptera in an earlier state, that is to say while still larva:*, 
figiues and describes certain cellular elements of the ovary, which subsequently become 
Purkinjean vesicles and surround themselves with yelk. 
The same explanation cannot as yet be applied to Limulus; but the figure given f 
closely resembles the appearance presented by the eggs of Spiders, in which, however, 
according to AVittich, V. Caeus, and Leuceaet, the original cell forms the Purkinjean 
vesicle, round which the yelk is subsequently deposited. AVe may therefore fairly wait 
for a confirmation of Gegenbaue’s observations before we unhesitatingly adopt the 
explanation which he offers of the mutual relations of the egg and the epithelial cells. 
If, however, we may admit that no essential difference has as yet been proved to 
exist in the eggs of Annulosa, so far as regards the relations existing between the Pur- 
kinjean vesicle and the original ovarian cell, it would still seem that in the relations 
betAveen the former and the yelk Lvo very different types of development must be 
recognized. 
* Zeits. f. AViss. Zcol. 1849, toI. i. p. 191. 
t Loc. cit, fig. 9. 
