IVORMS, CRAYFISH, CENTIPEDS, ETC. 159 



the single median eye, the mouth-parts, and five pairs of 

 legs (the last pair very small). There are no gills. Some 

 of the specimens, females, may have attached to the first 

 abdominal segment on either side an egg sac. Watch 

 the Cyclops capturing and feeding Paramcecium and 

 other microscopic animals. Make a drawing of Cyclops, 

 showing its parts. 



Water-fleas are extremely abundant, having great 

 power of multiplication. " An old Cyclops may produce 

 forty or fifty eggs at once, and may give birth to eight or 

 ten broods of children, living five or six months. As the 

 young begin to reproduce at an early age, the rate of 

 multiplication is astonishing. The descendants of one 

 Cyclops may number in one year nearly 4, 500,000,000, 

 or more than three times the total population of the earth, 

 provided that all the young reach maturity and produce 

 the full number of offspring." The Cyclops feed on 

 smaller aquatic animals, such as Protozoa, Rotifera, etc. 

 They in turn serve as food for fishes ; and because of their 

 immense numbers and occurrence in all except the swift- 

 est fresh waters they form the main food of most of our 

 fresh-water fishes while young. Many aquatic insect 

 larvae feed almost exclusively on them. 



Thousand-legged worms and centipeds. — Under 

 stones and logs, or buried in the soil, will be found at 

 almost any time of the year, in almost any part of the 

 country, specimens of thousand-legged worms. There 

 are two general types of animals belonging to this group, 

 the true thousand-legged worms, of which a common 

 representative is the large, blackish, cylindrical galley- 

 worm (fig. 116), that coils itself and emits an ill-smelling 

 fluid when disturbed ; and the flattened, usually brownish or 

 pale greenish slender centipeds or hundred- legged worms 

 (fig. 117). In both kinds the body is plainly composed of 

 rings or segments, but while in the centipeds there is but 



