THE TEREDO AND ITS DEPREDATIONS. 547 



been remarked that piles placed in dirty, muddy water, near drains, 

 for example, are protected thereby. The water should have, moreover, 

 a certain degree of saltness; the teredo cannot live in brackish water; 

 that is a point to which we shall return later. 



The teredo continues to grow in the wood ; while the gallery which 

 it forms presents near the surface a diameter of only one-quarter to 

 half a millimetre, it enlarges little by little, until it reaches a diameter 

 of five millimetres and more ; as regards his length, and consequently 

 that of the tube which incloses him, we have sometimes found it to be 

 thirty to forty centimetres. He never goes upward more than half-way 

 between the flow and ebb of the tide ; although the teredo is thus, for 

 a short time, partially above the water, yet it appears that the wood 

 holds a sufficient amount of moisture to sustain his life temporarily. 



The researches of Kater have still further shown, what had already 

 been remarked by Sellius, that the teredo can hibernate in the wood, 

 and that it is those individuals, thus preserved, which in the spring go 

 through with all the phenomena of reproduction i. e., the formation of 

 eggs, fecundation, development, and expulsion of the young. 



The part of the external integuments which constitutes the man- 

 tle deposits a calcareous matter, forming an interior lining to the 

 gallery in the wood (Fig. 12,/*); between this calcareous casing and 

 the body of the animal there remains a space sufficient to prevent 

 any inconvenience, at least during the act of respiration ; for it is 

 possible that when the teredo absorbs water, which serves for respira- 

 tion, his body is distended, and fills exactly the calcareous tube. The 

 form of this tube, secreted little by little, corresponds exactly with 

 that of the gallery, which has been slowly perforated in the wood ; it 

 has the appearance, also, of a series of rings placed one against the 

 other. As the animal progresses, a new ring is added to those which 

 existed before, so that when the tube is closed at its extremity by a 

 calcareous film, its length represents the total length of the animal 

 (Fig. 12, b to c). Among the segments of the tube, those which are 

 nearest the surface of the wood are the oldest and hardest ; in the in- 

 terior of the wood, where the gallery ends (Fig. 12, g), the calcareous 

 ring, newly formed, is at first soft, flexible, and of slight consistency ; 

 later, it becomes solid, and closes up the tube, as has been remarked 

 by Sellius. In the variety of teredo described by us, we have never 

 observed the formation of two openings surrounded by calcareous 

 matter, situated side by side, like an eight placed sidewise, 00, * and 

 serving as a passage for the siphons, as described by Deshayes. 



The calcareous tube, once formed, constitutes for each teredo his 

 own abode, where he isolates himself from his companions, and has 

 nothing to fear from their close proximity. One never sees a teredo 

 pierce the tube of another. The tubes make their way side by side, 



1 Some Oriental varieties have this form. I have seen them at the Boston Institute of 

 Technology, with solid tubes one and a half inch in diameter. Translator. 



