CRAYFISH, LOBSTERS, SPIDERS, AND INSECTS 135 



lobster weighing more than five pounds, while formerly 

 individuals were common that weighed much more. 



Cyclops. — This crustacean is common ia pond water 

 aquaria and is large enough to be seen with the naked eye. 

 It is free-swimming and, on account of its rapid, jerky 

 movements, it is called a water flea. The shape of the 

 animal is shown by 

 Fig. 72. The single 

 eye ia the middle of 

 the head suggested 

 the name "cyclops." 

 The antennules, which 

 are large, constitute 

 the principal organs 

 of locomotion. The 

 female carries the 

 eggs in sacs attached 

 to the sides of the 

 body. 



Barnacles. — These 

 are crustaceans that 

 were formerly thought 

 to be moUusks. They 

 are found in salt 



Fig. 72. — Cyclops : e, egg clusters. 



water, attached to piles, floating timbers, rocks, etc., and 

 are one of the promiaent causes of foul ship bottoms. 

 There are both stalked and sessile barnacles, the former 

 being known as "goose" barnacles and the latter as 

 "acorn" barnacles. 



The stalk, when present, is a flexible stem, or peduncle 

 covered with a finely wrinkled, dark-colored skin. It 

 bears the body of the barnacle at its free end (Fig. 73), 



