248 Modifications in Egg of the Medusa, &c. By M. A. Giard. 
having completely followed the preliminary phases he has given a 
false interpretation of the appearances observed. He considered 
that the ova of Cyanea were provided with a vitelline membrane of 
a considerable thickness, and pierced by a very large number of 
pores leading from without inwards, such, said he, as we find in 
the ovum of certain mammals—perhaps in all—and also in the 
ovum of many Teleostean fishes, where these pores have a much 
more considerable dimension. It is evident that these pretended 
pores are nothing else than columns of a clearer protoplasm to 
which we have already referred. Thus equally fall to the ground 
Harting’s supposition regarding the physiological function of these 
pores, that they may serve as channels for the respiration of the 
ovum, and also perhaps for the passage of the spermatozoa 
inwards. 
The preceding observations were conducted at Wimereux during 
September 1875. They were part of a series of researches not 
yet completed on the development of Medusz, and I decided to” 
publish them now because they seem to me to acquire a generality 
and an importance much greater than I at first supposed, thanks to 
the magnificent investigations of Weismann upon the ovum of the 
Daphnoidz (Clodocera).* 
Weismann has observed a process very like that which we have 
described, in the formation of what he calls the shell (schale) of the 
winter egg, in the genera Polyphemus Sida and Daphnella. It 
is remarkable that in this case, as in that of the Meduse, the egg 
underwent a tolerably long incubation in a special medium fur- 
nished by the maternal organism. 
The excretion of hyaline vesicles, which takes place from the 
entire surface of the vitellus in the ovum of Rhizostoma, may in 
other animals be limited to a portion of the surface. The pheno- 
menon then will have the appearance of a sort of excreted globules. 
One may—in the presence of this process—ask if the phenomena 
frequently pointed out, of rejection of a certain part of the vitellus 
at the moment of the maturation of the egg, should be regarded 
as equivalents in all animals in which they have been observed. 
Biitschli has in the clearest manner shown that the corpuscles de 
direction of the egg of Lymnzxus, Succinea, Nephelis vulgaris, 
and of Cucullanus elegans, arise by the process of cellular division. 
I may add that it is the same in Sulmacina Dysteri and in 
Spirorbis. In these various animals the excreted corpuscles have 
the value of rudimentary cells, having an atavic signification, and 
cannot be suitably styled refuse corpuscles (corpuscles de rebut). 
This term may, on the other hand, be applied to non-cellular 
* Weismann, “ Zur Naturgesch. der Daphnoiden” (‘ Zeitschrift fiir Wiss. 
Zoologie,’ XX VILL. Band, 1 and 2 Heft). 
