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. 
Daphnia, Mull., 
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 eve 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 lynceus, a small black spot, in the form of a point, which 
Muller took for another eye. This is also the opinion of 
Ramdohr, and, as he has discovered it in daplinia sima , it 
might be possible that this character was common to this sub- 
genus and the lyncci, although but little visible in the different 
species. Schoefter 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 known. Without speaking of those who have especially 
occupied themselves with microscopic researches, four most 
profound naturalists, Schocffer, Ramdohr, Straus, and Jurine 
the elder, — but the third more particularly, — have 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 
