j 74 INTRODUCTION TO ZOOLOGY. 



from man what lie had wrested from the ocean. Fortunately, 

 they, a few years after, totally abandoned that island, from 

 causes unknown, but suspected to be from their not being 

 able to live in that latitude when the winter was rather 

 severer than usual."* 



Owing to the general use of metal sheathing, the Teredo is 

 now nearly extinct on the British coast. The last account of 

 its ravages was one in 1834, relative to the injury it had 

 caused to the piers of Portpatrick, in Wigtonshire.f 



It is occasionally the. pleasing duty of the naturalist to 

 direct attention to some of the many examples where there 

 springs from "partial evil, universal good;" and perhaps the 

 Teredo, notwithstanding the evidence of its destructive powers, 

 might, if the whole truth were known, be ranked among tho 

 number of our benefactors. Mr. R. Ball has remarked to us, 

 "that but for the maligned Teredo, the sea would be so 

 covered with floating logs of timber, as to be to some extent 

 iinnavigable ; that the rivers of warm latitudes would be 

 choked up by the accumulated driftwood at their mouths, and 

 that their fertile banks would, in many cases, be converted 

 into morasses." 



On one occasion, on our northern coast, a piece of the 

 carved and painted woodwork of some unfortunate vessel was 

 flung up by the waves as we strolled along the beach, and 

 never shall we forget the interest with which we examined 

 the numerous perforations of the Teredo. The animals were 

 still living in the galleries which they had excavated, and 

 Avhich were lined, throughout all their windings, with a smooth, 

 white, shelly secretion. While all had applied with effect the 

 curious auger- shaped valves by which their perforations are 

 made, none had interfered with the progress of his fellows. 

 Almost in every instance,- when the borings approached too 

 close, their direction had been changed, and contact thus 

 avoided. It was strange to look upon this piece of drift 

 timber, the sport of the wind and waves, and reflect upon the 

 little world of animated existence it contained, and the skill 

 and perfection shown in the structure of their sea-borne 

 dwellings. 



* Dr. Jolmston, in 1820. Mig. Nat. Hist. vol. ii. page 23. 



f Win. Thompson, in Edinburgh New Phil. Journal. Jan. 1835. 

 The same gentleman has since recorded in Annals of IS T itt. History, Sept 

 18-i7, its occurrence at Ardro.--.uan, Ayrshire. 



