- 41 - 



ascidians, sponges and other low forms of creation; but it is 

 of no sort of use to the Pinna. 



If the creatures here described seem to be the embodiments 

 of the principle of stability, the cockle and scallop, on the 

 contrary, prove that not all the members of this family share 

 in difficulty of locomotion. 



The cockles or Cardium. are a genus with very numerous 

 and diversified species, and take their name from the shape of 

 their shell which is remarkable for its protruding spiral whorl, 

 and radiating ribs, often set with spines. The animal has a 

 long, rounded, bright red foot, of which it makes a very pe- 

 culiar use. Fixing it firmly on the ground, it stiffens it by 

 swelling, and then bounds forward for several feet. This jumping 

 is a very unexpected feat for a shellfish. The animal can also 

 sink deeply into the sand with surprising velocity by rapidly 

 extending and contracting its foot , the point of which being 

 hooked serves as an anchor. Cockles are much prized in the mar- 

 ket, and are caught in immense quantities on the English coast. 



The Scallop (Pecten), the largest species of which is the 

 Pecten jacobaeus, or pilgrim's scallop, has been used from 

 old time to decorate the hats or cowls of pilgrims, and belongs 

 to the best-known members of the whole group. It has one 

 round and one flat valve with radiating ribs. On the thicker 

 edge of the mantle are numerous short feelers and eyes, which 

 can be seen when the valves are open, the eyes glittering like 

 gems. They probably serve to guard the edges of the shell. 

 This animal makes movements as surprising as the jumping 

 of the cockle. It darts about in the water with arrowlike swift- 

 ness by opening and shutting its valves in quick succession ; as 

 soon as the movements cease, the animal falls to the ground. 



The most important and best known of all shellfish is the 

 oyster, Ostrea edulis. Its irregular, fiat, leafy and ugly shell, 

 which is generally fastened by its thick side to some stone or 

 piece of wood, is known to everyone. The animal itself effects 

 the adhesion by means of a secretion that penetrates through 

 the shell, and as the animal grows, the surface of adhesion is 

 enlarged. The oyster is remarkable for the retrograde formation 

 of its foot after it has fixed itself, and for being hermaphrodite, 

 which is the case with very few shell fish. The same individual 

 generates both the sperma and eggs. The number of the latter 

 is enormous, and is calculated by many naturalists at several 

 millions. The young oysters remain in the shelter of their pa- 

 rents' mantle until their shells are far enough developed for 



