12 
Transactions of the Society. 
parent. But bow it can do this is a puzzle. Neither ovary appears to 
have any connection with the cloaca, and the young rotifer seems to be 
in the body-cavity outside of the closed tube which passes from the 
cloacal outlet to the lower stomach. I have suggested* that the long 
thread which passes from the posterior end of the ovary towards the 
cloaca, may really be not a muscle, as is usually supposed, but 
the collapsed oviduct ; and that when the ovum becomes detached 
and seems to fall into the perivisceral cavity, it does not really do so 
but simply stretches out over itself the delicate membrane investing 
the ovary ; for the collapsed oviduct, which is a prolongation of this 
membrane, would at once yield to the slightest pressure, and accommo- 
date itself to the increasing size first of the ovum, and afterwards of 
the embryo ; while the extreme tenuity of the membrane may have 
caused it to escape notice when expanded over the young. However, 
this is only a guess ; for I have never seen any such membrane, and 
the difficulty is still waiting for its explanation. 
The next point is the frequent presence of spermatozoa in the 
perivisceral cavity. It is as perplexing to explain how they get into this 
cavity, as how young Rotifer vulgaris gets out of it. Coitus has been 
seen to take place in several species of Rotifera , and by various ob- 
servers ; and with the exception of Dr. Plate, all observers agree that 
it takes place at the cloaca, into which the oviduct opens. Neither the 
oviduct, nor the cloaca, is known to have an opening into the perivisceral 
cavity, and yet the spermatozoa in several species have been seen 
in that cavity, adhering to the outside of the ovary. How did they 
get there ? t 
There may, perhaps, be minute openings in the oviduct through 
which the spermatozoa can pass into the perivisceral cavity, but I 
* ‘ Rotifera,’ i. p. 103, footnote. 
f Dr. Plate describes experiments in which he has seen several males (in 
number varying from two to eight) having intercourse at the same time with the same 
female. He describes them as firmly fastened by the penis to various parts of her 
body ; and he asserts that the penis bores through the body-wall, anywhere, and ejects 
the spermatozoa, and the rod-like bodies which accompany them, into the body-cavity. 
Further on, however, lie qualifies this statement by saying that he never could 
find any traces of an opening in the cuticle, at the spot where copulation appeared 
to have taken place ; that the penis appeared to be glued on outwardly ; and that 
finally he believed that it was the stiff bristles of the penis which penetrated the 
cuticle, and gave a passage to the spermatozoa. 
It is not necessary to comment further on this strange theory than to say, that 
Gosse has seen intercourse take place at the cloaca in the case of Brachionus pala ; 
M. E. F. Weber in that of Diglena catellina ; and Mr. J. Hood, not only in Floscularia 
ornata , Synch feta gyrina , Euchlanis tri'.uetrc, and Melicerta tubicolaria , but also more 
than a score of times in Hydatina senta itself. 
Mr. Hood further states, in the letter with which he has favoured me, that the 
female Rhizota (whose copulation he has often witnessed) “ draw themselves up in 
their tubes, so as to bring the orifice of the cloaca above the upper edge.” He also 
says that Hydatina senta copulates while clinging with her foot to some confervoid 
filament, but Synchseta gyrina copulates while swimming. 
The duration of contact, according to Mr. Hood, is from forty seconds to two 
minutes in Hydatina senta , and three to three and a half minutes in Floscularia 
ornata. 
