Belding. — Conditions Regulating Clam Growth 125 



utilized in forming the shell, a process as essential to 

 growth as the assimilation of food. The lime salts are 

 obtained from the water, — since it has been shown that 

 clams will grow out of sand, — and are transformed into 

 a suitable form for shell secretion in the body of the 

 clam. The assimilation of the calcareous salts depends 

 upon the temperature, the activity of the animal, the 

 quantity in solution and the current. 



Sanitary Agent. — The work of the current as a sani- 

 tary agent consists in removing decomposing matter, 

 silt and decaying organic material, thus preventing the 

 spread of disease and the destruction of thickly planted 

 beds. 



Water. — The composition of the water, organic and 

 inorganic, soluble and insoluble, and its physical charac- 

 teristics influence the growth of the clam. The soluble 

 constituents, chiefly the nitrogenous salts upon which 

 the miscroscopic food forms subsist and the lime salts 

 for the shell, indirectly affect the rate of development. 

 The insoluble material, such as silt and sediment of va- 

 rious kinds, tend to interfere with the feeding ol* 

 the clam, which starves itself by mechanically throwing 

 off both food and silt from its gills. The insoluble food 

 forms, on the other hand, are of value for the nourish- 

 ment of the clam. Likewise the physical characteristics 

 of the water, such as salinity, temperature, depth and 

 tide may influence the existence of the clam. 



Salinity. — The clam will grow in nearly all degrees 

 of salinity, even as great a range as from 1.004 to 1.024. 

 It can be transplanted from waters of low salinity to 

 high or vice-versa without apparent harm, an interesting 

 fact for the culturist, and in this respect is in striking 

 contrast to the oyster, which is affected by the slightest 

 change in salinity. 



Temperature. — Temperature is the great controlling 

 factor which regulates the growth, habits and existence 

 of marine animals, differentiating the fauna and flora 

 of one region from another. With the clam, temperature 

 explains the faster summer and the slower winter growth, 



