130 FIRST BOOK OF ZOOLOGY. 



mussels, oysters, and clams, possessing certain characters in 

 common, together form a natural group of animals. 



There are, however, many other animals which are not 

 insects, spiders, or myriapods, and still possess a body com- 

 posed of segments, and also have jointed legs, and these ani- 

 mals are to furnish the subject for the next lesson. 



CHAPTER XVII. 



CRAWFISH AND LOBSTER. 



120. THE fresh-water Crawfish, or fresh-water Lobster as 

 it is sometimes called, is very common in many of the West- 

 ern rivers. It may be collected in little pools by the river- 

 side, and kept alive for a long while in a jar of water. It 

 may be fed on fresh-water snails and the larvse of insects. 

 It would be well to keep the animal alive for a while, so 

 that its motions in swimming and crawling may be ob- 

 served. For the cabinet, it can be dried with the legs out- 

 stretched, or specimens may be preserved in alcohol. 



The general form of the body is much like that of the 

 salt-water lobster, differing, however, greatly in size ; the 

 crawfish varying from three to five inches in length, and 

 the lobster attaining a much larger size. 



The animal is divided into two regions, the body proper, 

 to which the legs and big claws are attached, and the abdo- 

 men, consisting of the jointed portion behind. The head 



