134 TEREDINID;E. 



lieve that the eroded material undergoes any chemical 

 change, either in the stomach of the Teredo or in the 

 passage outwards through its intestine, although in the 

 latter receptacle it is closely compressed. When it is 

 voided or expelled by the excurrent tube, and separated 

 in the water, it becomes a flocculent mass or pulp, like 

 that of paper, composed of extremely minute and fine 

 particles of an irregular size and shape, but still retain- 

 ing its fibrous structure. It does not exhibit any 

 appearance of having been digested. The notion that 

 the Teredo feeds on the wood which it excavates ori- 

 ginated in the lignivorous habit of the grubs of certain 

 insects. It was lately revived by Laurent to a qualified 

 extent. He tells us that the water, imbibed by the larger 

 siphon, holds constantly in suspension particles arising 

 from the decomposition of organic matter, as well as 

 living animal and vegetable bodies, and that these 

 particles, coming from outside, are united with the lig- 

 neous molecules which are produced by the wood being 

 rasped and continually softened or macerated by the 

 water, in order to form the usual food of the Teredines. 

 But, independently of what I have above stated with re- 

 ference to this question, the cases of Saxicava and the 

 Pholades must be considered. It can hardly be ima- 

 gined that these are stone-eaters. Sellius found that 

 the Teredo did not attack a pile below fourteen feet. 

 Further information is desirable as to the depth at 

 which it is capable of living. He observed that it 

 commonly follows the grain of the wood ; and that con- 

 sequently its tunnellings in fir and alder are straighter 

 and longer than in oak, which is tougher and more knotty. 

 It usually works round knots in a curved direction ; 

 but occasionally it drives right through them. The 

 odour emitted by the Teredo is different from that of 



