04 Beautiful Shells. 
nor spun, nor drawn out of the body, like the web 
of the spider, but produced in a liquid form, and 
cast in a mould which is formed by a groove in 
the foot, extending from the root of the tendon to 
the upper extremity; the sides of this groove are 
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 the 
foot, and applied to the object to which it is to be 
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 
