Microscopie Seaual Characteristics of Oysters. 37 
V.—The Microscopic Sexual Characteristics of the Ameri- 
can, Portuguese, and Common Edible Oyster of Europe 
compared. By Joun A. RyDER*. 
In the issue of ‘ Forest and Stream’ of November 30 just 
past, in an article by the writer, page 351, middle column, it 
is remarked :—‘I regard Davaine’s observations upon the 
histology of the reproductive organs [of the European oyster] 
as of little value, being made before the introduction of im- 
proved methods of investigation. His figures of the finer 
structural details have apparently been made from crushed 
fragments.” In passing this judgment upon Dr. Davaine’s 
work I have been severer than the state of the case demanded, 
as will be seen in the sequel, though I do not yet admit that 
his methods of research were what they should have been, 
for until now we have had no adequate description of the 
structures in question. Until recently I have maintained 
with reservations that the sexes in the European oyster were 
probably separate, as in the American; more recent investi- 
gation with more refined methods have proved to me that in 
this I was in error. In my article in ‘ Forest and Stream’ I 
also took occasion to refer to a statement in Gegenbaur’s 
‘ Klements of Comparative Anatomy,’ English edition, p. 380, 
where he says :—“ In the oysters we find an intermediate step 
toward a separation of the sexes, inasmuch as these organs are 
not active at the same time in the same individual; but the 
male and female organs alternately so.” The writer, in com- 
menting upon the above, then wrote, “ This quotation tacitly 
admits the unisexuality of the Huropean oyster, to which it 
evidently refers. The last part of the remark, however, is 
founded upon the slenderest kind of evidence—in fact, upon 
no evidence except a surmise, as such an alternate activity of 
the two parts is improbable | for obvious reasons | ; besides, it 
is not possible to demonstrate such an alternation of sexual 
activity in the same individual. As every one knows, the 
soft parts of an oyster cannot be examined without opening 
the shell, which necessarily makes the needed second obser- 
vation to confirm this alleged alternation of sexual activity a 
physical impossibility.” Iam now in a position to go still 
further, and to assert that the first part of the quotation from 
Gegenbaur is also erroneous, because we may find both eggs 
and spermatozoa in the same follicle at the same time. 
* From the ‘Bulletin of the United-States Fish Commission,’ March 14, 
1883, pp. 205-215. 
