22 
was 3.6 mussels per starfish per 24 hours. The rate at which the larger mussels 
were destroyed (Sept. 6th-Sept. 19th) was 1.2 mussels per starfish per 24 hours. 
The results of the experiment with the sea-urchin are given in Table VII. 
The rate at which the small mussels were destroyed (Sept. Ist-Sept. 5th) 
was 3.1 mussels per sea-urchin per 24 hours. The rate at which the larger 
mussels were destroyed (Sept. 6th-Sept. 17th) was 0.7 mussels per sea-urchin 
per 24 hours. ' 
SUMMARY. 
1. At St. Andrews the sea-mussel is preyed upon by the flounder, eel pout, 
Purpura, common whelk, round whelk, starfish and sea-urchin. 
2. Under experimental conditions the common whelk did not eat the mussels; 
the round whelk ate a limited number of small mussels; the Purpura, starfish 
and sea-urchin ate both small and large mussels freely. 
SECTION: IV. 
THE RATE OF GROWTH OF THE SEA MUSSEL (MYTILUS. EDUETS 
L.) UNDER VARIOUS INTERTIDAL AND FLOATING CONDITIONS 
AT ST. ANDREWS, NEW BRUNSWICK. 
During the summer of 1919 experiments were conducted at the Biological 
Station, St. Andrews, New Brunswick, to ascertain the rate of growth of the sea 
mussel (Mytilus edulis L.) under various intertidal and floating conditions. For 
these experiments the mussels were allowed to attach either to blocks of wood or 
pieces of rock (when rock was used, that having a rough “‘honey-comb”’ surface 
was selected). The most satisfactory wooden blocks used were approximately 
2.5 inches wide by 8 inches long and had narrow grooves chiselled on the surface 
to which the mussels attached. The edges of these grooves were left as rough 
as possible, to give the mussels a surface to which they could readily fasten 
themselves. The grooves also furnished some protection against wave action. 
The mussels used were from 8-12 mm. in length. These young mussels attach 
themselves readily. It was found that they would fasten themselves to the 
rocks in from three to six hours, but for their attachment to the wooden blocks 
from two to three days were required. While the mussels were attaching them- 
selves the blocks (weighted to prevent floating) or rocks were placed in aquaria 
and the mussels (measured) were placed over them with sufficient sea-water to 
cover them to a depth of two or three centimeters. The water was renewed 
frequently. Each day the mussels were left without water for periods of two 
or three hours. This appeared to facilitate their attachment and also prevented 
them becoming unaccustomed to exposure. 
Sets of mussels were placed under the following conditions: One set was 
suspended from the floating breakwater, the mussels being placed at various 
levels from the surface; another set was fastened to a pole anchored to the 
bottom and thus kept at an approximately constant distance from the bottom; 
two other sets were fastened to the wharf at various intertidal levels, one set 
being exposed to direct sunlight, the other being constantly shaded; another 
36 
