414 APPLIED BIOLOGY 



grown chamber. It lives in the Indian and Pacific oceans, 

 usually in deep water. Some specimens have been found 

 floating on the surface, and so Holmes's reference to sailing 

 may not be entirely poetic license. 



The paper nautilus (Argonaut) is a relative of the octopus. 

 Only the female bears the delicate, single-chambered shell, 

 perfect specimens of which are much prized by collectors. 

 According to an old fiction, the argonaut did not secrete 

 the shell but stole it from some other mollusk in order to 

 use it as a boat in which to sail, using its two expanded arms 

 as sails. Now it is known that the two arms help secrete 

 the shell and hold it over the animal. Very little is known 

 about the habits of this remarkable animal. (Look up 

 the classical story of the argonauts.) 



All these highest mollusks are exceedingly voracious and 

 destroy large numbers of fishes, other mollusks, and crus- 

 taceans. The squids can swim fast enough to pursue schools 

 of fishes. A species of European octopus frequently enters 

 the traps set for lobsters and crabs, and the fishermen find 

 only mangled remains of the crustaceans. 



The squids, octopus, cuttle-fish, and nautilus represent a 

 class of mollusks known as cephalopods (Cephalopoda), 

 meaning head-foot, referring to the fact that in the embryo 

 the head develops from tissue which forms the foot in other 

 classes of mollusks. 



342. Economic Relations of Mollusks. The value of 

 the oyster industry is enormous in America and in Europe. 

 Studies by zoologists connected with government laboratories 

 have vastly improved methods of propagating, and have made 

 it possible to raise oysters where they do not naturally 

 grow. Oyster beds are now regularly leased by states to 

 oyster-men, and oysters are artificially " planted." In many 

 places it is necessary to rake the sea-bottom with steam 

 dredges annually in order to bring the oysters to the surface 

 and free them from the destructive starfishes. The egg- 



