TWO YOUNG NATURALISTS. 295 



oak, has been known to give way suddenly after a 

 few weeks, being mined by these invisible workmen. 

 In Holland, especially in that part of the country that 

 is preserved from the invasion of the sea by means of 

 dikes, the damage caused annually by these molluscs 

 is very considerable. 



" These other smaller holes, that you see at the 

 end of the wood, are made by an enemy of the ship- 

 worm, which fact, however, does not prevent it from 

 being equally our enemy. It is a crustacean, and the 

 selfish rascal would wish to have the monopoly of 

 destroying our artificial marine constructions. It is 

 the Limnoria terebrans. Our captain knows it well, 

 only he gives it another name, calling it, I believe, the 

 gribble." 



"Yery good bait for fishing-lines," sententiously 

 remarked the fisherman, pulling at his pipe. 



" That is all my find, except a Spongia oculata, one 

 of the few kinds of sponges found in the Channel, all 

 of which, moreover, are quite small. In warm seas, 

 sponges, on the other hand, sometimes attain enor- 

 mous dimensions. Witness the colossal sponge pre- 

 served in the museum at Havre, which was obtained 

 about thirty years ago under circumstances that are 

 worthy of being narrated. 



"As they were disembarking on to a lighter in 

 some port of Mexico I have forgotten which one 

 some cases of machinery imported in a vessel from 



