Anchoring Mollusks. 217 



new." He knows that stormy weather would result in his 

 emigrants being driven on shore ; so he chooses his time, that 

 the mussels may spin their cable and anchor securely. The 

 owner of piers also requires to tend the crop of mussel care- 

 fully, so that they may cover the wooden piles, and thus protect 

 them from the attacks of the boring shells. Some people 

 think that they are useless on the wooden piers, and con- 

 sequently scrape them off, considering that they destroy the 

 piles, and eat into the wood. 



Let it not be understood that the pedicle of the lampshell 

 and the byssus of the mussel perform the same function. The 

 pedicle, like the byssus, anchors the shell, but, unlike the 

 byssus, assists the pedicle in closing and opening the shell. It is 

 a fleshy cable, composed of fibres which are contractile. This 

 cable is attached at one end to the stone by a kind of glutinous 

 substance, and at the other to the upper or ventral valve. 

 Within a little distance from the foramen, or little hole through 

 which it passes into the shell, muscles are attached. These join 

 on to the pedicle near to the point of emergence, and are also 

 attached to the dorsal valve by the other end. The hinge of 

 the shell is at the foramen. When the animal is at rest, and 

 not disturbed, the pedicle is uncontracted, and the shell open. 

 The cable being at its longest range, allows the shell to hang 

 free, and to have a pretty wide range ; but whenever danger 

 approaches instantly the pedicle contracts, the shell by that 

 action shuts, and at the same time darts backward a little 

 towards its anchorage, out of the way of the intruder. The 

 pedicle contracts, and the muscles which are attached to the 

 pedicle contract at the same moment, and the shell is fast 

 closed, to be opened when danger is past. 



In the mussel the byssus acts no part similar to this. When 

 once it is spun it is lifeless. The visitor to the seashore will 

 find that it is made up of a great many small threads, which 

 have taken a very firm hold. These are connected with the 

 interior of the shell, and are extremely strong. The question 

 suggests itself, how are these threads spun, and how do they 

 fasten to the rock ? The mussel has no spinnarets like the 

 spider or the silkworm. That there is a sticky secretion no 

 one can doubt ; but of what it is composed, and how it is 

 secreted, is yet to be discovered. A Glasgow naturalist has 

 observed the process of placing the cable, which may be briefly 

 described. The foot was protruded, fat and fleshy, and touch- 

 ing the side of a glass jar, it remained for a time in contact. 

 After withdrawal nothing was noticed for a moment, but then 

 slowly a little thread became visible, and the first thread of the 

 cable was laid, which was followed by another, and another, as 

 the foot touched the side of the glass. There must, we think, 



