384 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



the young Teredos but they gradually grow larger as tbey go deeper and 

 deeper iuto the wood, until they souietimes become ten inches or more 

 in length and a quarter of an inch in diameter, but the size is generally 

 not more than half these dimensions. The holes penetrate the wood 

 at first perpendicularly or obliquely, but if they enter the side of the 

 timbers or planks across the grain, the burrows generally turn horizon- 

 tally in the direction of the grain a short distance beneath the surface, 

 unless prevented by some obstruction, or by the presence of other 

 Teredo tubes, for they never cross the tubes of their companions or 

 interfere with each other in any way, and there is always a thin layer 

 or partition of wood left between the adjacent tubes. It is, however, 

 not necessary that they should follow the grain of the wood, for they 

 can and do penetrate it in everj^ direction, and sometimes not more 

 than half the tubes run in the direction of the grain, and they are often 

 very crooked or even tortuous. They rapidly form their burrows in all 

 kinds of our native woods, from the softest pine to the hardest oak, and 

 although they usually turn aside and go around hard knots, they are 

 also able to penetrate through even the hardest knots in oak and other 

 hard woods. The Teredos grow very rapidly, apiDareutly attaining 

 maturity in one season, and therefore, when abundant, they may 

 greatly damage or completely destroy small timber in the course of four 

 or five months, and even the largest piles may be destroyed by them in 

 the course of two or three years. 



The most abundant species in this region is the Teredo navalis (cuts 

 land 2; Plate XXVI, fig. 183, animal 5 Plate XXVI I, fig. 186, shell.) 



EXPLANATION OF THE CUTS. 



Fifj, I. Posterior or outer end of a living Teredo naralis, removed from its burrow ; 

 c, the muscular collar by which it adheres to the shelly linino- of its burrow ; p, the 

 shelly "pallets" which close the aperture when the animal withdraws; t, the two 

 retractile siphon-tubes which project from the hole when the animal is active. 



Fig. 2. Anterior end and shell' of the same ; s, the front part of the shell ; /, the 

 foot or boring organ. 



This is the same species that has attracted so much attention in 

 Europe, during nearly two centuries, on account of the great damage that 

 it has done, especially on the coast of Holland. Nevertheless no full 

 description of the animal of this species has yet been published, nor 

 any satisfactory figures of the soft parts. 



When removed from its tube (see Plate XXVI, fig. 183) the animal is 



