inland fisheries. 27 



2. Kate of Burrowing. 



Among the habits which are of economic importance, either in 

 view of clam-culture or of replenishing the natural beds, the 

 habit of burrowing deserves a conspicuous place. In their early 

 life the clams are free-swimming animals, but soon " set," and after 

 they are several weeks old will never again thrive, however well 

 they may be protected, unless they are embedded in the soil. The 

 first attempt at burrowing may be made as soon as the clams quit 

 the swimming habit, or it may be postponed for a month or two, 

 according as they happen to fall upon good ground or to set upon 

 some object at a distance from the soil. At any time during the 

 first two months of their existence the clams all have a remarkable 

 capacity for rapid burrowing, a capacity which decreases gradually 

 as the individual grows older. Indeed, the necessity for burrow- 

 ing is greater in the small individuals, for they cannot go deep and 

 they are frequently washed or dug cut. 



The experiments which are given below in tabulated form were 

 made for the jDurpose of ascertaining (a) how much injury is done 

 by continually digging up clams which are not noticed by the 

 digger, or are not larg-e enough to eat ; and (b) under what condi- 

 tions it would be feasible and practicable to sow clams rather than 

 to plant them, in case one undertook clam cultivation on a large 

 scale. 



The first table records the experiments made at various times 

 during the summer, and under many varying conditions. 



