INLAND FISHERIES. 43 



same kiud and placed iu the same locality as some of those in 

 which other clams died earlier in the season. 



Comparing the results in experiments 20-23 with one another, 

 the average increase per week varies from 29 per cent, to 73 per 

 cent., and the difference in growth at low tide and high tide with 

 other conditions exactly similar is brought out iu the clearest 

 possible manner, namely, the per cent, of increase per week in the 

 box at high tide are 29 and 42 ; iu the box at low tide they are 69 

 and 73. 



The next two experiments (24-25) are also very instructive. The 

 clams in these two were from the same lot. In experiment 24 the 

 clams were put in a small box about . 18 inches deep, with a few 

 inches of sand in the bottom, and the box was suspended near the 

 surface of the water at the house-boat. The average increase per 

 week is only 31 per cent. In experiment 25 the regulation shallow 

 box was used, but was lowered 8 feet below the surface. In this 

 box the increase was 60 per cent, per week. These two experiments, 

 in my oi^iuion, demonstrate two points clearly : (1) That clams 

 will thrive at a considerable distance below the surface, if other 

 conditions are favorable ; and (2) that an apparently slight inter- 

 ference with the free circulation of water over the clams, like that 

 occasioned by the high sides of the box in experiment 24, makes 

 vast differences in the rate of growth — probably by decreasing the 

 food supply. 



Experiments 26 and 26a may be described as one, since 26a is 

 only a continuation of the previous experiment. 



These clams belong to the " artificial set " described on page 

 26. They were gathered from the small box on the shore, having 

 been precipitated from the water while in the free-swimming con- 

 dition. They were transferred on August 14th to a shallow sand-box 

 suspended about a foot beneath the surface at the house-boat. 

 The growth was more rapid than in anj- clams thus far described. 

 When j)lanted, 1,302 specimens made about three-quarters of a pint, 

 and at this rate 3,474 would have made a quart (see Fig. 1). On 

 September 20th the average weekly increase was 352 per cent. 



