30 
Tidal Pool Series. 
The tidal pools used in this experiment were shallow pools in the intertidal 
zone at the Biological Station. In Table XIV. are recorded the height above 
low-water datum, the surface, depth, etc., of the various pools. The temperature 
observations of July 21st were taken to ascertain the maximum temperature of 
the water in the pools during the experiments. July 21st was a bright sunny 
day and one of the hottest of the summer. Low water occurred at noon, thus 
giving the water in the pools every opportunity to become warm. The final 
temperature reading for each pool was taken just before the incoming tide 
entered it. With one exception (pool 9) this was the highest temperature 
recorded for each pool. In pool 9 it was lower than the earlier reading. This 
was due to the fact that in the morning and early afternoon the pool was exposed 
to the sun, but in the late afternoon it was shaded. The temperature of the 
incoming tide was 13.7° C at 4:18 p.m. Pool 3 was surrounded by sea-weed 
(Fucus) and a small amount was about pool 2... The other pools were free from it. 
The mussels used for this tidal pools experiment were allowed to attach 
to pieces of rock sufficiently heavy to remain in the pools without shifting their 
positions. The first set was put out (unprotected) in the pools July 4th. The 
Purpura destroyed all those in the lower six pools so that it was necessary to 
put out a new set. In Table XV. are recorded the results for the upper three 
pools of the first set. 
TABLE XV. 
Showing rate of increase in length of Mytilus edulis L. during first tidal pool series experiment 
n 1919. 
Pool 7 8 g) 
Bont in feet of pool above low water datum..»..,........,..... 183 19.3 20.0 
Risckbee Sepoutunspoolsjulyalden aan cece ee eee e eee eee ees ? 64 Pa 
Naber FECOVELEU SE pts gl Orr eather oe eevsaacs nite aie eo Bem bv Ze 55 pgeaaes 
2 ae LECOVered: Sept Ll Ona as seep cus ser eaters kara aitenscounre eietiae trees P 85.9 2.9 - 
foe length/in am. when isétouts|ully hie satire ccs ae serie el 11 11 Ries 
en - mm. Sept. Fite “a DEN ate Sterne aut rhe ee 14.3 ye gee 
eee increase in length in mm. rom July 17 to Sept. 10, 2.e., in Se 
BI ACAV IS. coh Pele egtd ord tose ec iesRasetyt ok CMe. chale ptioe ae Sates Rsk She heere ees 3.3 3.3 4.6 
peo increase in length in mm. per day from July 17 to Sept. 10.) 0.061 0.060 “0.084 
Mussels in tidal pools were feeding as shown by carmine in water. 
A second set was placed in the pools August 5th; of these the lower six 
were protected by cages of wire netting. This proved effective, except in the 
case of pool 3. It was found necessary August 20th to provide a fine meshed 
44 
