THE JOINTED-FOOT ANIMALS 



165 



Fig. 91. Daphnia, a water flea. 

 (Much enlarged) 



After Forbes 



Caprella. Probably one of the strangest-looking free forms 

 to be found in the sea is the little, brown Caprel'la geomet'rica 



(Fig. 90). It lives among 

 seaweeds, on which it can 

 be discerned with diffi- 

 culty. 



Water Fleas. Water fleas 

 (Daph'nia) have the body 

 inclosedinashell(Fig.91). 

 The feathery antennas are 

 used for swimming. The many different species of water fleas 

 are among the most abundant animals in lakes and rivers. 

 Many kinds of fishes feed upon these minute crustaceans. 

 The eggs and young are carried inside the 

 shell at the back of the body. 



Cyclops. Any fresh-water pond will af- 

 ford millions of specimens of the genus 

 Cy' clops (Fig. 92), and the sea contains 

 species of the same genus in such num- 

 bers that they with allied genera form 

 a large part of the food of many fishes, 

 and even some species of whales find in 

 them an abundant food supply. Their 

 powers of reproduction are so enormous 

 that it has been estimated that the de- 

 scendants of one Cyclops may number, 

 in one year, 4,500,000,000 individuals. 

 Though microscopic in detailed structure, 

 on close observation it is easy to see them 

 darting spasmodically through the water 

 in aquariums. A single compound eye in the middle of the 

 head gives them their name, in reference to the race of 

 mythical giants of Sicily. Two pairs of antennas, used in 

 locomotion, extend from the front of the head. The legs are 



Fig. 92. Cyclops. 

 (Much enlarged) 



After Claus 



