252 CRUSTACEA. 



ten minutes. The male, first placing 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 approximating 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. Jurine 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. magna 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 proceding 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 are 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 vinnter ; 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 Daphniae. 

 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 fact, 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 depth 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 proportion to the projection of the shell which 

 covers the body, an increase of its size impeding their movements. 

 According to Straus, their food consists exclusively of small parcels 

 of vegetable substances which they find at the bottom, and frequently 

 of Confervpe. They always refused the animal substances he pre- 

 isentcd to tlicm. He repeatedly saw them swallow their own faeces, 



