68 Lessons in Zoology. 



wonderfal machine in the top of the head. As if the 

 lobster had not jaws enough for tearing and chewing, he 

 has teeth inside his stomach, by which his food is so finely 

 ground that it will pass through a strainer of little hairs 

 into the back part of the stomach. 



The heart, a six-sided, spongy organ, which sends the 

 purified blood from the gills over the whole body, lies 

 under the carapace just behind the transverse groove on 

 the back. We have now seen that the carapace covers 

 and protects the most important part of the lobster's oody, 

 that containing the gills, the stomach, and the heart. 



Very young lobsters are beautiful, transparent little 

 creatures, that swim about at the surface of the water, 

 and are quite different from 

 their parents. Fig. 5 repre- 

 sents one magnified, while A 

 shows its natural size. 



A lobster's shell once 

 formed never increases in 

 size, and like a boy's jacket, 

 must be thrown away when 

 he has outgrown it. This is the way the lobster pulls 

 himself out of it : First, the shell splits here on the back 

 between the head- thorax and the abdomen, or down the 

 middle of the head-thorax, or sometimes in both places ; 

 then the poor fellow wriggles and twists till he gets his 

 head and legs out of their sheath, when with one pull he 

 frees the rest of his body. The new shell is formed be- 

 fore the old one comes off, but is very soft and loose, so 

 that the body can grow to fill it. This shell hardens and 

 thickens in a few days, but in this short time the lobster 

 has grown as much as he will until he moults again. 



