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HOW DO WE CLASSIFY ANIMALS? 



or food material, are glued fast to the swimmerets of the female, 

 where they develop. The young cling to the swimmerets for 

 several weeks after hatching. 



North American lobster. In structure the lobster is almost 

 the counterpart of its smaller cousin, the crayfish. It is highly 

 sensitive to changes in temperature, and migrates from deep to 

 shallow water, or vice versa, according to changes in the tempera- 

 ture of the water. The food supply, which is more abundant 



L. W. Brownell 



A rock crab. Crabs differ mainly from crayfish in having the abdomen much reduced. 

 Crabs molt, or change their shells, with great frequency when they are young, but 

 rarely after they are fully grown. 



near the shore, also aids in determining the habitat of the lobster. 

 As it is the color of the bottom and as it passes much of its time 

 among the weed-covered rocks, it is able to catch living food, 

 even active fishes falling prey to his formidable pincers. It 

 moves around freely at night, usually remaining quiet during the 

 day, especially when in shallow water. It eats some dead food 

 and thus is a scavenger, as is the crayfish. 



Several other relatives of the crayfish are the crabs of various 

 species, used for food, on our eastern and western coasts ; the 

 shrimps and prawns, thin shelled and small ; the fiddler crab, well 

 known to boys and girls of the eastern coast, and the sea-spiders. 



