42 Mr. J. A. Ryder on the Microscopic 
peculiar nucleus of the ovules at once distinguishes them from 
the elements which later break up and become the sperma- 
tozoa. Apparently every phase of the spermatogenetic pro- 
cess is under way in the follicles, while more or less nearly 
mature ovules may be adherent to the walls of the same 
tubules. In some specimens I find the tubules to contain 
nothing but ova, with little or no trace of spermatoblasts; in 
others, again, both classes of products may be present in about 
the same condition of maturity. In still others little else but 
spermatozoa are to be found, but, adherent to the walls of 
the follicles, cells are to be found which have the nucleus so 
characteristic of the more mature ovules. These, I am in- 
clined to believe, are the representatives of what will later 
become ova, and not the representatives of spermatoblasts. 
It is a singular fact that the spermatozoa have a tendency in 
O. edulis to cling together in masses of about a uniform size. 
Though the spermatic particles which compose these masses 
are somewhat separated from each other, 1f compressed to- 
gether they would evidently form a body about the size of the 
spermatoblasts from which they were derived. Later they 
tend to break up and form a more homogeneous granular mass 
at the outlet of their parent tubule, where the latter joins the 
outgoing efferent duct. While it is true that some sections of 
O. edulis show little evidence of the presence of any thing else 
but the product of one sex, it appears to me that there is suffi- 
cient evidence of the hermaphrodite character of the genera- 
tive glands of the species presented by a pretty large series of 
sections taken from about fifty individuals from different 
localities along the coasts of Wales, Scotland, England, 
France, Holland, and Germany. Sometimes a portion only 
of a section will be hermaphroditic, showing that different 
parts of the generative glands of the same animals may be of 
different sexes. The result of this arrangement is that it is 
scarcely possible for the eggs to escape impregnation by the 
milt generated alongside of them, and we may, I believe, 
fairly assume that Ostrea edulis is a selt-fertilizing herma- 
phrodite. 
The condition of things in the generative tubules of Ostrea 
virginica and angulata is very different, as may be gathered 
from the following account. In the first place I have never 
found any evidence of hermaphroditism either in the living 
animal or in sections of the reproductive organs. The mode 
of pressing out the spawn from the gland and ducts of O. vir- 
genica, and the physical test used to determine the sex of the 
products in practical work during the last season, afford the 
most positive demonstrations of the unisexuality of that species. 
