296 



THE POPULAR EDUCATOE. 



found smoothly and beautifully lined with a white hard china- 

 Jike material, which chemical analysis has shown to consist of 

 ninety-seven parts of carbonate of lime and three parts of 

 animal matter. The thickness of this hard crust or shell has 

 been computed at Jjth of an inch. The external orifice might, 

 without careful search, escape observation, as it is generally \ 

 hidden by marine growths which usually flourish in situations ! 

 favourable to the well-being of the teredo, and is much smaller ' 

 than the inte- 

 rior of the tube. 

 In fact, the 

 outer portion of 

 the pipe is but 

 barely large 

 enough to give 

 passage to the 

 two small tubu- 

 lar processes in 

 which the crea- 

 ture may be said 

 to be equally 

 divided. Figs. 

 2 and 3 show 

 the teredo both 

 in its shell and 

 ou t of it. Many 

 of these worms 

 men-sure as 

 much as eight 

 inchcsinlength, 

 and when in 

 their tubes ap- 

 pear to com- 

 pletely fill tliom. 

 They, however 

 diminish consi- 

 derably in size 

 when removed 

 from the tim- 

 ber, from their 

 throwing out a 

 considerable 

 quantity of 

 sea-water from 

 their internal 

 organs. When 

 exposed to light 

 and air, at the 

 head of the 

 worm are found 

 two concave 

 shell-like sub- 

 stances, united 

 by a strong liga- 

 ment, and to 

 these shells the 

 boring powers 

 of the worm 

 have been at- 

 tributed. Sir 

 Everard Home, 

 in speaking of 

 the proboscis 

 of the teredo, 

 says, that as 

 this proboscis 

 has no ori- 

 fice there is 



reason to believe that it adheres to the wood, acting as a 

 centre-bit, while the animal is at work with the shell, and thus 

 the canal in the wood is perfectly cylindrical. It has not 

 (infrequently been asked whether the teredo bored into wood 

 in order to feed on it. Our observations have led us to the 

 conclusion that it derives no nourishment whatever from the 

 timber it is engaged in penetrating, but rather that, like the 

 pholas and serpula before described, it needs a protecting and 

 sheltering tube in which to dwell, whilst its support is drawn 

 from amongst the countless myriads of organisms which fill the 



sea surrounding its abiding-place. That this is the case will 

 appear probable when we take into consideration that the body 

 of the living animal and the shell covering it will be found of 

 equal bulk and greater specific gravity than the woody substance 

 which is removed in making the tube. Here again we are of 

 opinion that it is not alone the boring shell which cuts away 

 and removes the solid timber. The Teredo gigantea, a species 

 found in the Eastern seas, although living in a shell constituted 



exactly like that 

 of the Teredo 

 navalis of our 

 own coasts, 

 bores his tube 

 in soft mud, 

 where the so- 

 called boring 

 or centre - bit 

 mode of opera- 

 tion is perfectly 

 needless. Al- 

 though it is dif- 

 ficult to ascer- 

 tain precisely 

 by what train 

 of laws the 

 shell-bearing 

 borers effect 

 their marvel- 

 lously curious 

 excavations, it 

 is easy enough 

 to convince one- 

 self of the 

 alarming extent 

 to which the 

 ravages of these 

 never-wearying, 

 indefatigable, 

 yet destructive 

 creatures ex- 

 tend. There 

 appears little 

 doubt that the 

 Teredo navalis 

 has been intro- 

 duced from 

 warmer cli- 

 mates into our 

 seas. However 

 that may be, his 

 acclimati sation 

 has been fully 

 achieved, and he 

 now abounds. 

 Although insig- 

 nificant in di- 

 mensions, it 

 would be diffi- 

 cult to find 

 any creature 

 amongst cre- 

 ated things 

 which causes 

 the same a- 

 mount of de- 

 struction to 

 valuable pro- 

 perty as the 



much-dreaded "ship-worm" (Teredo navalis). Ships, boats, 

 piles, dock-gates, and submarine wood-work of all kinds are 

 hopelessly ruined by it ; and although fabulous sums of money 

 are from time to time expended in order to check his ravages, 

 little can be done to control them. 



The magnificent floating dock at Sebastopol, destroyed by the 

 allies at the conclusion of the Crimean war, was constructed at 

 a vast cost by the Russian Government, in order that such ships 

 as were required to undergo repair, etc., might, by being caused 

 to float in fresh water, escape the destruction caused by tho 



