2/0 CLADOCERA ; DAPHNIA, OR WATER-FLEA. 



jecting animal matter when offered. There are several curious 

 points, relative to the propagation of these little animals, which 

 are worthy of notice. After the eggs leave the ovaries, they re- 

 main in a large cavity between the body and the shell ; here they 

 usually attain their complete development, the young coming 

 forth into the world in a form very nearly resembling that of the 

 parent. From the transparency both of the eggs and of their 

 containing envelope, the whole process of development may be 

 distinctly seen. At first the eggs are quite round, and seem as 

 if made up of a multitude of minute globules. The shape then 

 alters a little, becoming oval ; and these globules augment in 

 number ; but as yet no trace of any body is perceptible. A little 

 afterwards, we see a black spot in the centre, which is the eye, 

 and which is the first organ visible. The other organs then begin 

 to show themselves ; but it is not until near the end of the fourth 

 day, that any motion is perceptible. They come forth into the 

 world, at the end of the fifth day, with the tail curved up within 

 the shell ; and very shortly after birth, this tail may be seen to 

 spring forth with a sudden jerk, and to assume its natural posi- 

 tion. In a short time afterwards, the animal acquires the perfect 

 form, and it speedily increases in size, throwing off its envelope, 

 and acquiring a new one, at short intervals. In summer these 

 moul tings are frequently seen to be performed every two days ; 

 but in colder weather, several days elapse between them. They 

 do not cease with the full growth of the animal, but continue 

 during its whole life. The purpose of this may be, to prevent 

 the animal being injured by the tendency of its shell to become 

 overgrown with parasitic Animalcules and Confervas ; for weak 

 and sickly individuals may be frequently seen so covered with these 

 growths, that their motion and life are soon arrested, the animals 

 apparently not having strength enough to throw off their envelope. 

 880. After the third or fourth moulting, the young Daphnia 

 begins to deposit its eggs in the cavity of its back ; these may 

 be frequently seen there, as early as the tenth day of its separate 

 existence. Soon after the young are born, another moulting takes 

 place ; and the egg-coverings, which have been left in the cavity, 

 are thrown off with the shell. In a very short time afterwards, 



