THE ANIMAL SERIES 387 



mostly for locomotion, while the front pair, which are 

 very much enlarged at their extremity, are used for grasp- 

 ing and cutting food and also for carrying the food to 

 the mouth. It has two long projecting antennae which 

 serve as feelers and also for smelling. It moves forward 

 slowly while in search of food, but in case of danger it 

 moves backward swiftly a motion caused by rapid, 

 forward jerks of its tail and seeks protection under 

 stones or other objects in the water, or in the bottom of 

 its hole if it happens to be a land crayfish. It reproduces 

 by depositing eggs, 

 which are carried 

 about on the under 

 side of the body until 

 hatched. The young 



crayfish which come 



- Al A CRAYFISH MOVING BACKWARD 



from the eggs also 



attach themselves to little projections, called swimmerets, 

 on the under side of the body of the parent, until they 

 are able to find food and care for themselves. 



The thorax of the crayfish is a bone-like armor which 

 extends from the back around to the bottom of its body, 

 but the lower edge is not grown to the body of the crayfish. 

 Just under this bony covering are feather-like projections 

 called gills. The blood flows through these gills and takes 

 oxygen from the air in the water. The crayfish causes a 

 current of water to flow over these gills in order to keep 

 a fresh supply of oxygen going into its blood and carbon 

 dioxide coming out. 



The North American lobster is a close relative of the 

 crayfish. It grows in the salt water along the Atlantic 

 coast in great numbers and is a valuable source of food. 

 Various states have different laws regulating the size 



