The Growth of the Soft Clam 301 



may be expressed in weight or in cubic contents. The 

 latter plan was chosen, and the determination made by 

 displacement in water. A clam one inch long displaces 

 approximately 1.6 cubic centimeters of water; one two 

 inches long displaces about 1 1 cc., or nearly seven times as 

 much; while an individual measuring three inches dis- 

 places 43 cc., and is about twenty-seven times as large as 

 the first. With a table of such facts, inches were trans- 

 formed to cubic centimeters, and the increase in volume 

 expressed in percentages. 



Again, clams all of the same length when planted will 

 vary somewhat in size after a year's growth. When 

 these were dug and measured, they were segregated into 

 sets according to size. The number in each set was 

 counted, the sets arranged in a series, and the arith- 

 metical mean of the series calculated. Then the volume 

 of the mean of the series was compared with the volume 

 of the clams when planted, and the percentage of in- 

 crease in volume determined. 



Perhaps a specific example of the employment of this 

 method will be less opaque than the foregoing statement. 

 In a bed planted on July 13, 1899, the planted clams 

 were one and one-half inches long. They were removed 

 on July 4, 1900, the length of each obtained, and all 

 were arranged in sets, and the sets in a series. The 

 mean length of the series, expressed in eighths of an inch, 

 was 20.952, or nearly two and five-eighths inches. The 

 volume of a clam one and a half inches long is 4.5 cc. 

 That of an individual two and five-eighths inches in 

 length is 32 cc. Therefore the increase in volume in this 

 case is about 688 per cent. 



Many thousand clams were placed in beds in a locality 

 in which there was practically no current, the only ex- 



