44 Mr. J. A. Ryder on the Microscopic 
from May 26 to June 1, 18 per cent. were hermaphroditic, 
and of the remaining 82 per cent. one half were egg-bearing, 
the other half sperm-bearing. In none were the sexual pro- 
ducts completely mature. From these observations I con- 
clude that the eggs and spermatozoa do not develop simulta- 
neously but successively in the sexual gland; that sperma- 
tozoa may be developed very soon after the discharge of the 
ova, and that probably one half of the oysters of one locality 
during a breeding-period produce only eggs and the other 
half produce only spermatozoa.” To the same effect are the 
statements of Lacaze-Duthiers ; but Davaine seems to have 
first noticed the peculiar aggregations of spermatozoa in oval 
masses in Ostrea edulis. Brooks thinks “ Gerbe’s statement, 
that among the 435 European oysters one year old he found 
35 with young, 127 with ripe eggs, and 189 with ripe semen, 
seems to be sufficient to show the incorrectness of Lacaze- 
Duthiers’s conjecture that the functionally male condition 
precedes the functionally female condition.” 
This is about the state of the controversy at present in re- 
gard to the breeding-habits of Ostrea edulis. ‘The only 
authority, as far as 1 am aware, who distinctly takes the 
ground that eggs of this species are fertilized in the repro- 
ductive organs is Horst, who says, “‘ Not only do the embryos 
pass through their first stages of development within the 
mantle-cavity of the adult, and impregnation occurs internally 
instead of externally, but it may also be said that the eggs 
and spermatozoa come into contact in their passage out of the 
generative glands.” It is barely possible, indeed probable, 
if my memory serves me rightly, that Davaine has put similar 
observations upon record. Horst also distinctly asserts that the 
normal development of the embryos of Ostrea edulis cannot 
take place outside of the parent. M. Berthelot, according to 
Mr. Brandely, has discovered that the fluids in the mantle- 
cavity of O. edulis contain albumen in a notable proportion, 
upon which the young are supposed to be nourished. Mr. 
Brandely has found, by direct experiment, that in the case of 
QO. angulata it is possible to artificially impregnate the eggs. 
His attempts to fertilize the eggs of O. edulis with the milt 
of O. angulata and vice versa were unsuccessfully repeated at 
different tires for the last two years. I am now also uncer- 
tain in regard to the identity of the species of which Lieut. 
Winslow succeeded in artificially impregnating the eggs at 
the mouth of the St. Mary’s River, in the Bay of Cadiz, Spain, 
which he says were natives, the variety having existed and 
flourished in the bay for as far back as could be remembered, 
I quote his description of the specimens he used in his experi- 
