ORDER BRANCHIOPODA. 345 



their intercourse, which lasts, at most, from eight to ten 

 minutes. The male, placed at first on the back of the female, 

 seizes her with the long filaments of his anterior feet ; then 

 getting towards the inferior edge of her shell, and approximat- 

 ing his own to its ajjerture, he there introduces these fila- 

 ments, as well as the hooks or harpoons of those feet; he 

 then approaches his tail to that of his companion, who at 

 first rejects his addresses, runs with great swiftness, carry- 

 ing him along with her, but ends by yielding. Some small 

 bodies, in the form of grains, of a green, rose, or brown colour, 

 according to the seasons, composing the ovaries, ascend 

 gradually into the matrix, and there become eggs. Jurine 

 observes, that the males of the D. Pulex are of small num- 

 ber, in comparison with the females, that in spring and 

 summer hardly any are to be found, but that they are less 

 rare in autumn. 



About eight days after their birth, the young daphniaa 

 change their skin for the first time, and subsequently continue 

 the same operation every five or six days, according to the 

 greater or less elevation of temperature ; not only the body 

 and the valves, but also the gills and the setae of the oars, are 

 stripped of their epidermis. It is not until the third moulting, 

 that these Crustacea begin to reproduce ; they at first lay but 

 a single egg, then two or three, and increase progressively, 

 even up to fifty-eight in one species, fD. Magna). In a 

 single day after the laying, the female changes skin, and in 

 the teguments which she has abandoned, are found the shells 

 of the last laid eggs. In a moment afterwards she lays again. 

 The young of one and the same birth, are almost always of the 

 same sex, and it is rare to find in a birth of females, two or 

 three males, and vice versa. But in five or six births during 

 the summer months, one at the most, consisting of males, 

 takes place. Individuals are often to be met with, whose 

 teguments are of a milky white, opake and thick, without the 



