34 OUTLINES OP NATURAL BISTORT. 



to their being attached to the legs, the animal's respiratory- 

 process depends very much upon its moving about, since the 

 movements of the legs contribute considerably to the 

 brinf'ino- in of fresh water to the chambers in which the 

 gills are contained. 



The nervous system, lastly, has the form of a series of 

 nervous masses placed along the lower surface of the 

 body, and united with one another by longitudinal cords. 

 The first pair of these masses is placed above the gullet, 

 and the cords which unite them with the next pair pass 

 on each side of the gullet, so that the gullet is surrounded 

 by a "nerve-collar." 



The Lobsters are exclusively found in the sea; and 

 though they can live a considerable time out of the water, 

 they are essentially aquatic animals. They are exceed- 

 ingly voracious, and are usually captured by means of 

 "lobster-pots," or baskets baited with some kind of 

 carrion or garbage. When injured, or even if greatly 

 alarmed, they throw off one or both of the great claws ; 

 but these appendages soon grow again, though not so 

 large as before. They also cast their shells periodically, 

 since the resisting nature of this covering does not allow 

 of their growth. When fresh they are very brightly 

 coloured ; but they turn to a uniform and brilliant red 

 when boiled. They are most ordinarily about a pound in 

 weight, but they sometimes grow to three or four pounds. 



Recapitulation of Essential Characters. — The 

 skin is hardened with lime and horny matter, so as to 

 form a resisting shell or "crust," within which the internal 

 organs are protected. The body consists of a succession 

 of distinct rings or segments placed one behind the other ; 

 and each segment may carry a single pair of jointed 

 appendages. The animal breathes air dissolved in water, 

 and usually has breathing-organs in the form of gills. 

 The nervous system consists of a chain of nervous masses 

 placed along the lower surface of the body. Less essen- 

 tial, though highly distinctive, are the characters that the 

 true legs are from five to seven pairs in number, that the 

 segments of the abdomen carry appendages, that there are 



