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the commencement of the organized tube, in which the animal is to 

 be developed. When secured beneath this opaque screen, the little 

 miner is no longer exposed to observation ; but if his cell is opened at 

 the end of a few days, it is found that it has secreted a new shell, 

 larger and more solid than the original one ; it is the shell of the 

 adult animal. 



The young Teredo, which feeds on the raspings of the wood, increases 

 rapidly ; it passes first from a spheroid form to an elongated shape, 

 and when its body can no longer be contained in the shell, it projects 

 beyond the edge, and would find itself naked were it not protected by 

 its membranous sheath, which adheres to the walls of the ligneous 

 channel, now the dwelling-place of the animal. 



The process by which a creature soft and naked like the Teredo 

 should break into a solid piece of the hardest wood so quickly, and 

 destroy it with so much facility, was long a mystery. Until very 

 recently, the shell was looked on as the implement of perforation. 

 But in that case the shell should preserve certain traces of its action 

 upon surfaces so resistant as oak and fir ; but the shell, on the con- 

 trary, is perfect, with no signs of friction. On the other hand, the 

 muscular apparatus of the Teredo is not calculated to put the shell 

 into rotatory action, were the process a boring one. It does not 

 seem therefore possible to attribute these perforations to a simple 

 physical action. 



Some naturalists have suggested, in explanation of this phenomenon, 

 that the animal is furnished with the means of secreting a liquid 

 capable of dissolving the woody fibre. This has been met by the 

 statement that, in whatever way the wood is attacked, whether the 

 gallery is excavated with or across the fibre of the wood, the groove 

 is as exactly and neatly cut as if it had been perforated by the 

 sharpest tool, and that a corroding dissolvent could not act with this 

 regularity, but would attack the harder and more tender parts un- 

 equally. This objection, which M. sQuatrefages opposes to the idea of 

 a chemical solvent, appears to us to admit of no reply. But, while 

 opposing unassailable reasons against two theories, the learned author 

 does not leave us without a very reasonable explanation of a very 

 puzzling phenomenon. "Let us not forget," he says, "that the 

 interior of the gallery is constantly saturated with water; conse- 

 quently all the points of the walls which are not protected by the 



