500 



Marvels of the Universe 



A WATER FLEA. 



Cyclops, the one-eyed, is very abundant in fresh water and inhabits the muddy ooze of the pond. The single eye is placed in 

 the middle of its forehead. Note the curious egg-pouches of the female. \\ ith the rest of the Water Fleas, it is a very minute 

 creature, about the tenth of an inch long. 



near the surface on dull days, but retiring to the lower layers in bright sunny weather ; sometimes 

 on looking down into such a pond a pale pinkish cloud will be observed, and on bringing some of 

 this up in a net or bottle, it will be found to consist entirely of a dense struggling mass of Daphnia. 

 Cyclops, on the other hand, so-called from his having but a single eye situated in the middle of his 

 forehead, like the giant of Greek mythology, prefers a soft muddy bottom in shallow water, while 

 the active, fussy little Cypris prefers to paddle about water-weeds. 



In Daphnia the body is enclosed in a shell-like carapace from which only the head and the 

 large branched swimming-arms project. The latter are not true feet, but are more comparable 

 to the " feelers " of lobsters ; the feet of Daphnia are enclosed, like the rest of the organs, 

 within the shell ; they are used to promote a constant stream of water towards the mouth, and 

 as this current brings the minute organisms which form the food of Daphnia, we may say that its 

 feet are used, not for locomotion, but merely to kick the food into the animal's mouth. Cypris 

 is even more completely enclosed within its shell, which in this case is hinged along the back, so 

 that it is really bivalve, like the shell of a cockle, and, like it, can be shut completely when at 

 rest. In both Daphnia and Cypris the shell is minutely sculptured with very fine lines. Should 

 it touch the surface of the water, the latter is at once thrown off as if off a duck's back, and the 

 unlucky swimmer is unable to get back beneath the surface until it reaches some object down 

 which it can climb and forcibly drag its shell down. In Cyclops the carapace is not so large and 

 the body and limbs are free. 



In the case of creatures like these, whose whole world is often a small pool or puddle liable at 

 ■one time to be frozen solid, at another, and more frequently, to be altogether dried up, conditions 

 which may perhaps be compared with those in which the Martians live, active existence is liable to 



