DIAPTOMUS. 223 



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 opercidum vulvte. 



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 vulvas, 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 Miiller, and are called by him the 

 lacinifs. 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 latimdatus. 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 Miiller, 

 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. 



