340 CLASS CRUSTACEA. 



procure but a very small number of individuals, this species 

 being rare in the environs of Geneva. But it appears that it 

 is very common in the marshes and ponds of the north, where 

 it forms very considerable troops. 



Daphnta, Miill., 



Have their oars always uncovered as far as their base or the 

 origin of their pedicle, as long, or almost as long, as the 

 body, divided into two branches, the posterior of which has 

 four articulations, the first very short, while the anterior has 

 but three. Their eye is small, or in the form of a point, and, 

 if we except some species, we do not see in front of it, as 

 in Ijnceus, a small black spot, in the form of a point, which 

 Mliller took for another eye. This is also the opinion of 

 Ramdohr, and, as he has discovered it in daphnia sima, it 

 might be possible that this character was common to this sub- 

 genus and the lyncei, although but little visible in the different 

 species. SchoefFer had already observed this spot. 



Although the organization of these Crustacea, from the 

 extreme smallness of the animal, would seem to escape the 

 inspection of the observer, yet there is scarcely any that is 

 better knowai. Without speaking of those w^ho have especially 

 occupied themselves with microsco])ic researches, four most 

 profound naturalists, Schoeffer, Ramdohr, Straus, and Jurine 

 the elder, — but the third more particularly, — iiave studied 

 these animals with the most scrupulous attention. If some 

 details of organization have escaped the last, the researches of 

 MM. Ramdohr and Straus supply that deficiency. Jurine, 

 besides, completes their observations as to habits, which, for 

 a long time, he most accurately traced and observed. 



The mouth is situated underneath, at the base of the bill. 

 We consider, with M. Ramdohr, as a hood of an elongated 

 form, the lower portion of the head, which M. Straus calls 

 labrum, and we apply this last denomination to the part 



