126 American Fisheries Society 



the warm water stimulating the assimilation of food and 

 the secretion of the shell while the cold water causes 

 the animal to become sluggish. 



Depth. — Little difference has been noticed in the 

 growth of clams suspended in sand boxes at various 

 depths, and since the habitat of the clam is between the 

 tide lines the question of depth is of little importance. 

 In enclosed bays the deeper layers of water do not always 

 have as good a circulation as the shallow waters, which 

 are disturbed by wind and wave action; but in the tidal 

 rivers the deeper waters have the stronger current. 



Tide. — Although the natural home of the clam is be- 

 tween the tide lines, submerged beds are occasionally 

 found below extreme low water mark and numerous 

 experiments in Rhode Island and Massachusetts have 

 demonstrated that submerged clams grow faster owing 

 to a longer feeding period. A series of beds extending 

 from high to low water mark shows a gradual increase 

 in growth as low water mark is approached. Assuming 

 that the clam feeds continually when under water, an 

 increased daily exposure materially lessens the amount 

 of food consumed, an assumption that is open to the criti- 

 cism that the clam may not feed continually and that 

 the lower beds have a better circulation of water. The 

 latter objection has been eliminated by parallel experi- 

 ments where the only difference was the exposure. 



Soil. — Soil is a less important factor in clam growth 

 than is commonly supposed and affects the growth in 

 two ways, indirectly by affecting the quantity of food, 

 and directly by affording a resting place. Soils vary 

 in their capacity as breeding grounds for the production 

 of the microscopic food forms, which multiply upon the 

 surface of certain flats. The direct action of the soil 

 is largely mechanical and the actual character affects 

 the shape, flavor and growth of the clam. Dr. J. L. Kel- 

 logg states that a tenacious sand (fine sand with a little 

 cementing mud) furnishes the best medium for the 

 clam, both from the standpoint of growth and easy 

 digging. Nevertheless clams grow in nearly every kind 



