302 



Our Food Mollusks 



change of water being in the rising and falling tide. In 

 July, pebbles and stones on the surface became coated 

 with a dense growth of sea-weed. Masses of dead eel- 

 grass, which were barely floated at high tide, also re- 

 mained on the beds for days at a time during the 

 summer. All of this must have interfered greatly with 

 the feeding of the clams, but in spite of the unfavorable 

 condition, the increase in volume was great, as is shown 

 in the following table : 



In order to present some tangible idea of this growth, 

 Figure 60 was prepared. The jar to the left contains 

 seventy-five individuals, each one and five-eighths inches 

 long. The other holds an equal number of the size of 

 the mean after a year of growth two and a half inches. 

 The increase in volume is 347 per cent. If clams much 

 smaller when planted had been chosen, the illustration 

 would have been much more striking. 



The following table shows the growth of several thou- 

 sand clams on a bed where the exchange of water was 

 much better than on the first, though not so good as on 

 some flats. Unfortunately most of the clams planted 

 here were smaller than those on the first beds, so that the 

 percentage of increase cannot be compared. Small 



