24 
blocks were at depths of 1, 2, 3, 6 and 9 feet respectively from the surface. The 
results of this experiment are recorded in Table VIII. Unfortunately the whole 
series was lost during the second week of October so that it was impossible to 
obtain the rate of the growth late in the season. 
TABLE IX. 
Showing rate of increase in length of Mytilus edulis L. during anchored pole series experiment 
in 1919. 
3) gel Saeae Reenter api car Se 11 12 13 14 15 16 ily/ 18 19 | 20 
Minimum. depth in feet from 
SUTSACE sR ten ee we Roeo as 2 | 3.16) 4.32) 5.48) 6.64) 7.80) 8.80) 9.80)10.80)11.8 
Number on block when set out 
PUTS Ae PE oie eet Rua ek 66 | 125 ? 85 | 119 | 85 72 | 95 |14.4] 0.8 
Number surviving Sept. 15..... 25 cA OLS LOM 2a 15 22 ee GG al GAs a2 eee 
Percentage surviving Sept. 15...|37.8 |80.8 ? 131.7 (63.8 25.8 |81.6 |67.3 |18.8 |- 12 
Average length in mm. when set 
RNR Aer hae, cas tod ces] OD 9 9 9 9} 10) > 200) “LO Tones 
—— ——* — | | ee 
Average length in mm. Sept. 15./16.8 |17.0 |16.3 |15.8 |14.9 |16.0 |16.3 |16.4 |15.3 
Average increase in mm. Aug. 4, 
CHD: WTO Note sce EN Pe 723128. 00| "78 166.8 1. 941"6.07| (628 sossal aes 
Number examined Sebt. 15.....} 10 27 PHY 8 17 5 19 11 2, 
Average increase in lengt in 
mm. per day Aug. 4-Sept. 15) 0.17/0.19 | 0.17} 0.16) 0.14) 0.14) 0.15) 0.15} 0.13 
no sample taken 
Average increase in length in 
mm. from Aug. 4-Oct. 18, 
Pele A GOLGAY Ss ke ovat deere oe 6.9 |11.0: |1272 |11.6 |13.9 
| 
Average increase per day in 
length in mm. from Sept. 15 
COREL PA ere ote ss nak oee net 0.091) 0.15) 0.19) 0.24 
From the results of this experiment it is evident that the most advantageous 
depth for the growth of the sea mussel is 1 foot from the surface. The irregularity 
which is contrary to this conclusion occurring in the rate of increase in length _ 
at a depth of 3 feet noted on August 4th, is probably due to the small number of 
measurements on which this rate is based. It will be observed also that, with 
the exception mentioned above, the rate of increase in length decreases as the 
38 
