Belding. — Conditions Regulating Clam Growth 129 



Thousands of acres of barren flats may be reclaimed 

 by such means as artificially directing the tidal currents, 

 seeding with small clams, covering soft soils with sand 

 or gravel, draining certain areas, and forming a tena- 

 cious surface by planting thatch on smooth current- 

 swept flats. Each flat represents an individual problem 

 and special methods must be adapted for each case. 



Summary. — In this paper I have endeavored to bring 

 out the following points: (1) The environment of a clam 

 is the result of many complex forces, some of which I 

 have enumerated, so interwoven in their action that it 

 is difficult to definitely determine their separate influ- 

 ences. (2) The existence of the clam depends essentiall3^ 

 upon three groups of conditions, the current, the water 

 and the soil, while the rate of growth from a practical 

 standpoint depends chiefly upon the current. (3) A 

 knowledge of the relative value of these factors is of 

 importance to the clam culturist. (4) The former pre- 

 vailing explanation that current achieves its result by 

 merely increasing the amount of available food is entirely 

 inadequate. The actual increase in the food forms by 

 no means accounts for the much greater growth, which 

 is evidently due to the increased powers of assimilation 

 of the clam either directly by the stimulation of the cur- 

 rent or indirectly by the supply of oxygen. 



DISCUSSION 



Mr. I>vdell, of Michigan: Is it possible for fresh water clams to 

 get into a pond unless the clams themselves are carried there? We 

 have a pond that was dug in the soil eight or nine years ago and it 

 is now filled with the fresh water mussels. 



President: The larvae of fresh water clams are temporary para- 

 sites on certain kinds of fishes. These larvae attach themselves to the 

 gills and fins of these fishes until they reach a certain stage of devel- 

 opment. Your fishes probably transferred the clams to the pond in 

 this stage, after which they dropped off and grew to maturity.* 



Prof. Dyche, of Kansas: What is the geographical distribution of 

 this species of salt-water clam? 



*See "Studies on the Reproduction and Artificial Propagation of 

 F>esh-water Mussels," by George Lefevre and Winnerton C. Curtis, 

 in Bulletin of the Bureau of Fisheries, Vol. XXX, 1910, pages 105-201, 

 plates 6-17. — Editor. 



