346 
CLASS CRUSTACEA. 
animals appearing to be affected by this modification. On 
the renewal of their testa, but slight traces of this alteration 
are perceptible, and those are manifested by rugosities. 
These Crustacea cease to reproduce, and to moult, on the 
approach of winter, and end by perishing before the com- 
mencement of the frosts. The eggs contained in the ephippia, 
which had been laid during the summer, disclose on the first 
return of warm weather, the following spring. The pools are 
then speedily repopulated with an infinite number of daphniae. 
Many naturalists have attributed the sanguine colour which 
these waters sometimes assume, to the presence of myriads 
of the Daphnia Pulex. But M. Straus declares that he never 
observed this fact, and that at all times this species is but 
slightly coloured. In the morning and evening, and even 
during the day, when the sky is cloudy, the daphniae remain 
habitually at the surface of the water. But during the very 
w T arm weather, and when the sun shines strongly on the 
pools or stagnant waters which they inhabit, they sink 
into the water; and remain at a depth of six or eight feet, or 
more. Frequently, not a single one is to be seen at the sur- 
face. They swim by little springs, of greater or less extent, 
according as their oars are more or less long, and as the 
buckler, which covers the front of their body, projects out- 
wards, more or less, the largeness of this projection being 
capable of impeding their movements. According to M. 
Straus, their nourishment consists exclusively of small por- 
tions of vegetable substances which these animals find at the 
bottom of the water, and very often of confervae. They con- 
stantly rejected the animal substances which he presented to 
them. He has frequently seen them swallow their own ex- 
crements, drawn in by the current of water produced by the 
action of their feet, and which conveys their ordinary aliment 
towards their mouth. The hooks which terminate the ex- 
tremity of their tail, serve to cleanse their gills. 
12 
