326 Our Food Mollusks 



which had been marked by tagged staples driven into the 

 ground. 



The results of six months of growth during the 

 warmer part of the year may briefly be stated as fol- 

 lows : — Continually submerged, quahaugs one and a 

 quarter inches long when planted, increased in volume 

 in one bed two hundred and twenty-two per cent, in six 

 months. It is possible that the increase might have been 

 somewhat greater here if the bed had not been almost 

 entirely surrounded by great numbers of oysters that con- 

 sume the same food. 



The increase was less in other beds in the same local- 

 ity. For example, clams one and three-eighths inches 

 long increased only seventy-eight per cent, in volume. 

 Here, however, the wire netting exposed above the bot- 

 tom had become the lodging-place of an abundant growth 

 of sea-lettuce (Ulva), which flattens down in a current 

 so as to prevent free access of the food-bearing stream. 

 The effect of this mat of sea-weed in preventing the 

 growth of hard and soft clams alike has been noted care- 

 full v in many cases. It should, however, cause little 

 trouble to the culturist, for it may easily be removed by 

 a little raking. 



Where everything seemed to have been favorable on 

 the beds between tide lines, quahaugs varying from one 

 and a half to one and a quarter inches in length showed 

 an increase in volume ranging from one hundred and 

 fifty-five to two hundred and fifty-five per cent. 



In 1904 extensive experiments on the growth of Venus 

 were begun by Mr. Belding for the Massachusetts Fish 

 and Game Commission, and these were carefully and con- 

 tinuously pursued for several years following. 



Mr. Belding has found that growth nearly ceases 



