^SSL.fprn^S^^^ Ovarian Egg of the SaccuUnse. 215 
lY. — Besearehes on the Constitution and Development of the 
Ovarian Egg of the Sacculinse. By M. J. Gerbe. 
The studies wliicli I have pursued for many years at Concarneau, 
on the development and the metamorphoses of marine animals, 
have led me to the discovery of a fact which seems to me to clear 
up a point, still very ohscure, in the history of the ovarian egg. 
In the ovule of a considerable number of species belonging to the 
divers classes of the animal series, besides the vesicle known to 
physiologists under the name of germinative vesicle, or vesicle of 
turkinje, we see a second vesicle, generally smaller, which occupies 
a position in the egg more or less near to the first vesicle. MM. de 
Wittich, Siebold, and Y. Cams, have pointed it out in the ovules 
of the common spider ; M. Balbiani has discovered it in those of 
the Myriapods, the Crustacea of the genus Oniscus, in Helix, the 
Frogs, in a large number of the Arachnida, &c. ; finally, M. Coste 
had figured it already in 1847, in the primitive ovule of the bird, 
immediately below the vesicle which forms the centre of the cica- 
tricule. What part, then, does this second vesicle perform ? Should 
we agree with M. Balbiani, in considering it as the true centre of 
the formation of the germ ? May it not, however, be destined to 
fulfil another function ? The question may be thoroughly resolved, 
it seems to me, by studying the ovule of those singular parasites 
known under the name of Sacculinse (Sacculina, Cavolini ; Pelto- 
gaster, Kathke), which are found adhering to the tail of certain 
Crustacea, notably Cancer moenas. In these parasites the reproductive 
organ which represents five-sixths of the entire mass of the animal, 
contains ovules of all ages, of which the different developmental 
phases can be traced from their origin to their maturity. Taken 
towards the central portion of the organ, these ovules, which are 
only six or eight hundredths of a millimetre in diameter, present so 
different a form from that usually observed in other animals, that 
it would be difficult to recognize their true character, if we did not 
see them pass from that state to a more advanced one, which allows 
of no doubt. They are then formed : (1) of two independent trans- 
parent vesicles, of nearly equal size, and nearly touching at one 
point of their circumference ; (2) of a general envelope (the vitelline 
membrane), which is very delicate, and compressed towards the 
point where the two vesicles face each other ; (3) of a minute quan- 
tity of colourless substance, very finely granulated, which separates 
the two vesicles from the enveloping membrane. The ovule, instead 
of being globular, is here bi-lobed, and, as it were, composed of two 
ovules placed back to back, and resembling each other in form and 
organization. 
