Tue ZooLocist—JuUNE, 1876. 4939 
of Von Hessling; and the accomplishment of such a result would 
be easily attained in the calm weather, with the least amount of 
disturbance in the water, usually prevalent at the spawning season 
of these mollusks. At the same time it is very evident that if this 
general transfer of the ova, after being fertilised in the water,does 
take place, the males will be the recipients and foster-parents of 
the eggs and future progeny equally with the females; which cir- 
cumstance perhaps throws some light on the hitherto much vexed 
question concerning the reputed hermaphrodite nature of a large 
number of the lamellibranchiate Mollusca. 
Whether in the oyster—assuming there to be two distinct sexes— 
the reproductive process is identical with what is here recorded of 
Modiolus, remains to be ascertained; though, on the other hand, 
it is also possible that the milt only is ejected into the water, and 
then drawn into the gill-chambers of the females to fertilise the 
ova, which would in this case not be released until the embryos 
are fully developed. The appearance of the “ white sickness” at a 
date considerably in advance of the black one, as evidenced by 
Mr. Austin, would under such circumstances be readily explained, 
being indeed a necessary and natural condition instead of an 
abnormal one, as this witness was disposed to regard it. That the 
white secretion, or “sickness” as it is called by the trade, is 
usually identical with the milt or male reproductive element 
throughout that group of the Mollusca which includes the oyster, 
was first pointed out by Prevost so far back as the year 1823, at 
which date he discovered and made known the separate sexuality 
of the genus Unio; these observations being still more amply 
and generally confirmed by the investigations of Wagner, Milne- 
Edwards and C. T. von Siebold. The genera Pecten and Cyclas 
are among the very few in which it has been satisfactorily demon- 
strated that the two sexes are combined in-the same individual,— 
that is, that they are truly hermaphrodite,—which information has 
been mostly derived from the painstaking and valuable labours of 
M. lLecaze-Duthiers. 
The experiences here related concerning the propagation of the 
genus Modiola seem to be by no means confined to the same group 
or even class of animals. It was, in fact, the first observation of 
almost parallel phenomena in connection with the well-known 
tubicolous annelid, Serpula contortuplicata, that led at once to an 
easy solution of those associated with the mollusk. One morning 
