inner cage for the mussels of this pool. 
dl 
A number of the mussels were removed 
from the pools September 11th, while a number were left in the pools until 
October 7th, except in the case of pool 3. 
the Purpura that it was necessary to remove them all from this pool September 
11th. The results of this experiment are recorded in Table XVI. 
TABLE XVI. 
So few survived the depredations of © 
Showing rate of increase in length of Mytilus edulis L. during second tidal pool series experi- 
ment in 1919. 
Pool 1 2 3 4 5 6 7 8 9 
Height in feet of pool above 
low water datum........ Cote Opo | kaO oso 1h. 2° 16.0 1s 19.3" (S20n0 
Number set out in pool Aug. 5 150 68 112 86 69 51 69 60 65 
Number recovered Sept. 11.../143 51 18 57 61 49 65 46 57 
Percentage recovered Sept. 11.| 95.3 | 75 16.0 | 66.2 | 88.3 | 96.0 | 94.2 | 76.6 | 87.7 
Number again set out in pool 
SS Tara Achar an ahe: ish asy seats 103 32 0 32 23 30 41 46 24 
Number recovered Oct. 7..... 82 18 21 3 28 33 22 19 
Percentage recovered Oct. 7...| 79.6 | 56.2 65.6 °| 13.0 | 93.3 | 80.5-| 47.8 | 79.1 
Average length in mm. when 
SEE OUI PANES SO troy) aye cha 5 10.5 | 10.5 } 11 10) 6%), 10) SO 5a) 20. Ss) Age re 
Average length in mm. Sept. 11} 18.5 | 12.1 | 11.3 | 11.8 | 11.7 | 12.1 | 12.6-] 12.4 | 12:6 
Average increase in length in 
imme. trom vue. oo sept.|( 3-00) 1.65\7 O3io 2.3.) Bes) 16) 21 1290226 
1a 2.6%, ino” -dayss. ow 
Number examined Sept. 11...| 40 19 18 25 38 19 24 15 33 
Average increase in length in 
mm. per day from Aug. 5| 0.080) 0.046) 0.087) 0.036) 0.035) 0.044) 0.058) 0.054) 0.073 
COLDED tee Meee ra verevoetiaal 
Average length in mm. Oct. 7.| 14.1 | 12.9 1273 11258 113-0 >\1S-3) sO) Ase 
Average increase in length in 
mm. from Aug.5-Oct. 7 
BGx, Uh Gar GAYS cigiate cram os 3.6 | 2.4 fh Sp | 28 |e oe eae aoe m teens 
Number examined Oct. 7..... 82 18 21 2 28 33 22 19 
Average increase in length in 
mm. per day from Aug. 5 
TOOCE or eco aise ne 0.056} 0.038 0.028! 0.035! 0.049) 0.037; 0.040! 0.067 
45 
