94 Beautiful Shells. 



nor spun^ nor dmwn out of the body, like tlie "vrcb 

 of the spider^ but produced in a liquid form, and 

 cast in a mould -svhich is formed by a groovo in 

 the foot, extending from the root of the tendon to 

 the upper extremity ; the sides of this groove arc 

 formed so as to fold over it and form a canal, into 

 which the glutinous or sticky secretion is poured ; 

 there it remains until it has dried into a solid 

 thread, when the end of it is carried out by tho 

 foot, and applied to the object to which it is to bo 

 attached ; the canal is then opened through its 

 whole length to free the thread, and closing again. 

 is ready for another casting ; as if conscious how 

 much depends upon the security of his lines, the 

 animal tries every one after he has fixed it by 

 swinging itself round so as to put the threads 

 fully on the stretch. When once they are firmly 

 fixed, it seems to have no power of disengaging 

 itself from them; the liquid matter out of which 

 they are formed is so very glutinous, or glue-like, 

 as to attach itself firmly to the smoothest bodies. 

 The process of producing it is a slow one, as it 

 does not appear that the Pinna can form more than 

 four or five in the course of twenty-four hours. 

 When the animal is disturbed in its operations, it 

 sometimes forms these threads too hastily; they 



