262 



MARINE INVERTEBRATES 



annual catch on the Atlantic coast of North America amounts to 

 many millions of lobsters, the money value of which is very 

 large. 



H. americanus, the common lobster of the Atlantic coast. The 

 characteristic feature of the lobster is its enormously developed chelae, 



or pincer-claws, which are on the 

 first pair of walking- feet. Small 

 claws occur on the next two pairs, 

 and simple hooks on the remain- 

 ing two pairs. The appendages 

 on the abdomen are divided (bira- 

 mous). In the female they are 

 used, excepting the last pair, for 

 holding the eggs; in the male 

 they are greatly abridged. The 

 appendages on the next to last 

 segment are divided and broadly 

 flattened, forming with the telson 

 a powerful swimming-paddle. 

 The rostrum is very prominent, 

 and has a long, pointed end, 

 slightly upturned, and several 

 spines. 



The lobster belongs to the 

 creeping forms of the order; it 

 walks forward by means of the 

 ten feet, but swims backward by 

 using its caudal fin. It lives in 

 deep water on rocky bottoms, 

 hiding among stones, etc., but 

 frequents sandy shores as well. 

 It lives on dead and decaying 

 animal matter, and it would seem 

 strange that its flesh is so pala- 

 table, were it not that we know 

 that chemical combinations which 

 take place in the assimilation of 

 food make one kind as clean, 

 when transformed, as another. 

 All the crustaceans have a sim- 

 ilar dietary, being scavengers of 

 the sea ; yet fishes find them more 

 acceptable than other animal food, and fishes capable of capturing larger 

 prey subsist largely on the minute entomostracans described elsewhere. 

 The lobster is so large that it can easily be dissected, and will serve as a 

 type of the structure of Crustacea. In dissecting one can follow the 

 descriptions given of the anatomy of Crustacea on page 246, and will be 

 interested in observing the beautiful arrangement of the parts and their 

 adaptation to the uses they serve. 



Homarus americanus, American lobster ; male. 



