252 
CRUSTACKA. 
ten minutes. The male, first placinff himself on the back of the 
female, seizes her with the long threads of his anterior feet ; he then 
seeks the inferior margin of her shell, and a])j)roximating the aper- 
ture of his own to that of the latter, he introduces the threads, as 
well as the hooks of these same feet. He now brings his tail in con- 
tact with that of his companion, who at first, refusing to comply, 
flies with her amorous mate, but finally yields. Little granulated 
bodies of a green, rose, or brown colour, according to the season, 
gradually ascend into the matrix and become eggs. J urine observes, 
that the males of the D. pulex are but few, when compared to the 
number of females ; that they are extremely rare in spring and sum- 
mer, but less so in autumn. 
About the eighth day after they are hatched, the young Daphnia 
effects its first change of tegument, and repeats the same process 
every five or six days, according to the increased or diminished tem- 
perature of the weather ; it is not merely the body and valves which 
lose their epidermis, the branchiae and setae of the oars undergoing 
the same operation. It is only after the third change that they are 
fitted to continue their species. At first the female lays but a single 
egg, then two or three, gradually augmenting the number, which in 
the D. maqna amounts to fifty-eight. The day after she has pro- 
duced her ova, the female changes her skin, and in the teguments 
which she abandons may be found the shells of the eggs she has pre- 
viously laid. The next moment a new batch is produced. The 
young from each set of eggs are generally of one sex, and it is rare 
to find two or three males preceding from that which produced females, 
and vice versa. But in five or six of these broods, in the summer, one 
at most consists of males. Individuals are frequently remarked, 
whose integuments ai'e of a milky white, opaque and thickened ; they 
do not however appear to be affected by it, and on the renewal of 
the shell, but slight rugous traces of this alteration are perceptible. 
These animals cease to propagate, and no longer cast their skins 
on the approach of winter ; they perish before the extreme cold has 
arrived. The ova contained in the ephippia, and which were laid 
during the summer, are hatched on the first approach of the vernal 
heat; and the ponds soon abound again with countless Daphnise, 
Some naturalists attribute the occasionally sanguine tinge of these 
waters to the presence of myriads of the D. pulex, but Straus says he 
never remarked the faet, and that this species is at all times but 
slightly coloured. Morning and evening, and even during the day 
in cloudy weather, they keep on the surface ; but in the heat of sum- 
mer, or when the sun darts his rays directly upon the pools which 
they inhabit, they descend to the dejhli of six or eight feet; frequent- 
ly, not one is to be seen on the surface. Their mode of natation is 
by little bounds, of a greater or less extent, according to the length 
of their oars, and in ])roportion to the projection of tlie shell whicli 
covers the body, an increase of its size impeding their movements. 
According to Straus, their food consists exclusively of small parcels 
of vegetable sid)stanccs which they find at the bottom, and frequently 
of Conflu'vie. They always refused the animal substances he pre- 
sented to them. He rej)eatedly saw tliern swallow their own fleces. 
