EXCAVATORS. 343 



respects to that of the adult animal. It cannot be 

 that this shell is the instrument wherewith the per- 

 foration is executed, for it is very fragile ; and it 

 would surely show some signs of wear and tear, 

 which is never the case." 1 



It has been the source of much speculation, and 

 inquiry, how these animals, without powerful boring 

 organs, can make their tunnels in the hard wood. 

 Some have imagined that the animal secretes some 

 fluid which corrodes the wood, so that it may 

 easily be removed. Yet no one has been able to 

 prove the existence of such a corrosive fluid in 

 connexion with the animal. Professor Owen has 

 explained that it needs no corrosive fluid, but 

 that the muscular action of the mollusk is in itself 

 sufficient. 



By whatever method the boring may be accom- 

 plished, it is of more importance to discover how 

 some check to their ravages may be devised. M. de 

 Quatrefages has shown, by experiment, that this feat 

 may be accomplished. After they have attained 

 their adult state the Teredos live in secluded 

 galleries, hence some have imagined that each 

 individual is at the same time male and female, 

 whereas this is not the case, for they are of 



1 Moquin-Tandon's "World of the Sea," p. 193. 



