546 



THE POPULAR SCIENCE MONTHLY. 



design in the water ; at that time they were from eight to fourteen 

 days old, and, although very small, they resembled in every respect 

 older teredos. 



Teredos penetrate wood naturally by very small openings in a direc- 

 tion perpendicular to the surface (Figs. 12 and 15, C) ; then they gen- 

 erally turn about in order to follow the direction of the woody fibres, 



usually upward, but sometimes down- 

 ward. Although they do not enter into 

 the earth or mud, one generally finds 

 the first traces immediately above the 

 line of the mud in which piles are 

 driven ; it is at this point that piles 

 destroyed by the teredo generally break 

 off. 



''lit''' lP fISi When the teredos are lodged in a 



piece of wood, one recognizes them by 



very small holes on the surface, and the 



'Iftlf ' : .^!'|./; f'^^flSlt extremely delicate tubes which project 



from them (Fig. 12, e, d). These are 

 the siphons, only one of which shows at 

 first, the other appearing later. These 

 siphons are generally kept outside the 

 wood in the water, but the slightest 

 touch causes the animal to retract them. 

 One of them is shorter and larger than 

 the other, but they both seem to serve 

 for the expulsion of the fasces, which 

 largely consist of particles of wood 

 reduced to a very fine powder. It is 

 known that the teredo does not per- 

 forate wood for nourishment, but only 

 to procure a suitable abode ; the woody 

 substance, detached in the boring, 

 passes through the intestinal canal, 

 and then is expelled in the form of a 

 very fine white substance by one of 

 the siphons, generally, according to 

 M. Vrolik, by the shorter, but some- 

 times by the longer. The long siphon 

 appears to serve principally for the introduction of food, which consists 

 of infusoria, diatoms, and other inferior animalcula, which the sea-water 

 brings with it into the siphons. It is nevertheless still uncertain 

 whether the matters expelled through the longer siphon come directly 

 from the intestinal tube, or if they are first introduced from outside with 

 the inflowing water to be expelled again after a short sojourn inside. 

 The teredo requires for respiration a clear, pure water. It has often 



Fig. 12. Wood exposed from November, 

 1874, to September, 1876, in erib at Pier 

 No. 1, New York, North River, twenty- 

 five feet below mean low tide. 



