VENUS MERCENARIA 21 



Very briefly the following results will be described. Several 

 small beds, each with an area of i6 square feet, were laid out on 

 the gravel between tide lines. A group of these was separated by 

 an interval of 20 or 30 yards from another group. Most of these 

 small plots were within the boundaries of the oyster bed already 

 mentioned, but some were above the line of the bed, and a few 

 of them were dug clean. Others were not discovered by clam 

 diggers, and apparently entirely escaped molestation. 



In each of these small beds, clams all of a size were planted. 

 The number on a bed varied from 100 to 175. I would call particu- 

 lar attention to the fact that on the deeper beds, where the tide 

 currents were swiftest, larger stones were exposed, and there was 

 here an abundant growth of seaweed, which was not found farther 

 up on the beach. This always interfered seriously with the growth 

 of the clams. 



For example, on these beds w^iich were below the ordinary low 

 tide line, where we should expect to find the most rapid growth, 

 there was an increase in volume in clams iA| inches long, of 35^; 

 in those ly^ inches long, of 41;^; and in those i-^f inches long of 

 42^. I am all the more certain that this low rate of growth is to be 

 explained by the presence of the seaweed, because I had previously 

 had the same experience in a much larger experiment in the soft 

 clam. Fortunately, as I have already stated, a little labor by one 

 who is able to be on the spot during the entire year would prevent 

 this result. 



Some of the higher beds, however, which from the character 

 of the bottom were free from the weed, gave different results, and 

 show the possibihties of growth much better. On a bed only three 

 or four feet from ordinary high water line, there was placed on 

 July 6, 130 clams, i-^^ inches long. On Dec. 30, almost the entire 

 number w^as removed. Some had increased more than others. 

 The mean of the series was calculated, and showed an increase 

 of 255^ in volume in a little less than six months. 



^On another bed, somewhat lower, 150 clams ly^ inches long had 

 increased 157^ in volume. One of the things to be expected is that 

 clams of smaller size would show a relatively greater growth. It 

 has not been possible to make comparisons to demonstrate this 



