DIAPTOMUS. 
228 
the auricle. The pulsations of the heart are very frequent, 
from 112 to 120 in the minute. Underneath the first 
segment of the abdomen in the female, is the vulva, or 
external organ. It forms also the opening of the canalis 
deferens, and through it the ova pass into the external 
ovaries. Above this opening we see a triangular, reddish 
body, which Jurine calls the operculum vulva. 
In some specimens of this species, we occasionally see 
on each side of the abdomen two, four, or six elongated 
bodies, the direction of which is invariably backwards. 
In the females, to which sex they are principally confined, 
they are found adhering round the operculum vulvse, and 
when they have been noticed in the male, they have been 
seen adhering to the base of the posterior feet. These 
bodies were noticed by Muller, and are called by him the 
lacinice. He regarded them as some particular organs 
belonging to the animal, and they were considered by him 
as sufficient to constitute the individual possessing them 
into a distinct species, which he describes under the name 
of Cyclops lacinulatus. The use of these organs, how- 
ever, he was totally ignorant of. Jurine also observed 
them, and says, that at first he was disposed, like Midler, 
to regard them as peculiar organs, and that from their 
presence he was led to infer that the individuals charged 
with them were a distinct species. After very attentive 
observation, however, he found the number to be irre- 
gular ; he found them also occasionally in males, and he 
observed that they would separate spontaneously from the 
body of the animal. Not being able to discover any use 
for them, he conjectured them to be infusory animalcules. 
Jurine states, that it is in the months of March and April 
that these bodies are to be met with ; but the only time I 
have ever seen a specimen of Diaptomus with them at- 
tached, was in the month of October. It was taken from 
Yetholm Loch, in Roxburghshire ; but an accident occur- 
ring to the vessel in which it was placed, I was prevented 
from making any lengthened observations upon them. 
