378 INTRODUCTION TO CONCHOLOGY. 



of the whale and shark were similar to those of the Teredo 

 navalisj the skill and ingenuity of man would be almost 

 inadequate to counteract the machinations of such formidable 

 and persevering foes. 



Sea-worms have the same office assigned them in the 

 water as Termites have on land. These insects, which to a 

 casual observer appear solely occupied in spreading terror 

 and destruction wherever they advance, are nevertheless of 

 infinite importance to the well-being of mankind. They 

 consume decaying vegetable substances of various kinds ; 

 they also resemble common flies in their general operations — 

 those indefatigable little labourers, the pioneers of clean- 

 liness and order, who continually employ themselves in 

 perforating animal substances, and enabling the elements 

 speedily to decompose and dissipate them. Their operations 

 tend to elucidate those of the Teredines, with which it is 

 impossible to become so accurately acquainted, from the 

 nature of the element in which they subsist. We are, how- 

 ever, fully warranted in concluding, that, were it not for 

 their incessant labours, the mighty rivers of the tropics 

 would in time become impeded by the vegetable masses 

 and innumerable trunks and branches of large forest-trees, 

 which are continually carried into them ; and that a consi- 



