MOLLISCA ACEPHALA. 225 



in addition, with a singular apparatus for with- 

 standing the fury of the surge, and securing 

 itself from dangerous collisions, which might 

 easily destroy the brittle texture of its shell. 

 The object of this apparatus is to prepare a 

 great number of threads, which are fastened at 

 various points to the adjacent rocks, and then 

 tightly drawn by the animal ; just as a ship is 

 moored in a convenient station to avoid the buf- 

 feting of the storm. The foot of this bivalve is 

 cylindrical, and has, connected with its base, a 

 round tendon of nearly the same length as itself, 

 the office of which is to retain all the threads 

 in firm adhesion with it, and concentrate their 

 power on one point. The threads themselves are 

 composed of a glutinous matter, prepared b^^ a 

 particular organ. They are not spun by being- 

 drawn out of the body like the threads of the 

 silk-worm, or of the spider, but they are cast in 

 a mould, when they harden, and acquire a cer- 

 tain consistence before they are employed. This 

 mould is curiously constructed ; there is a deep 

 groove which passes along the foot from the root 

 of the tendon to its other extremity ; and the sides 

 of this groove are formed so as to fold and close 

 over it, thereby converting it into a canal. The 

 glutinous secretion, which is poured into this 

 canal, dries into a solid thread ; and when it has 

 acquired sufficient tenacity, the foot is pro- 

 truded, and the thread it contains is applied to 



VOL. I. Q 



