98 A NATURAL HISTORY OF THE SEAS 



Walton, discovered its value by mere chance. Being 

 cast away on the shores of a muddy bay off the coast of 

 Western France, he sought about making crude nets to 

 trap sea birds, fixing his nets with stakes driven into the 

 sand. The nets were usually covered at high water, and 

 in time he observed that myriads of small shells attached 

 themselves to the nets. Before long the shells reached 

 a noticeable size, and Walton, discovering the excellence 

 of their contents, took to cultivating them in this fashion 

 when he was finally repatriated. In this manner sprang 

 up a vast industry which is now widely carried on both 

 sides of the Atlantic. Of late years these shellfish are 

 placed in special purifying tanks prior to marketing, for 

 the better assurance of their being free from detrimental 

 germs. The Common Mussel is the chosen host of the 

 Pea Crab noticed in a previous chapter. 



It should be mentioned that all bivalves commence 

 life as minute larvae, hatching from eggs. The larva 

 has minute shells and between them a pair of flaps armed 

 with lashing hairs, which propel the little creature through 

 the water and also carry food into its interior. In time 

 it sinks to the sea-bed and takes to a crawling or sedentary 

 existence. 



The Date Mussels (Lithodomus), though not unlike 

 Common Mussels, do not anchor themselves by means 

 of a tuft of threads, but tunnel into solid rock, usually 

 limestone, by means of a specially secreted acid. The 

 covering of horny material protects the Date Mussel's 

 delicate shell from its own corrosive secretions. Tourists 

 in Italy are shown a Temple of Ceraphis, the pillars of which 

 are riddled with these mussels, clear evidence that the 



