TEMPERATURE AND SHELL MOVEMENTS OF OYSTERS 
5 
amount of time open show clearly parallel fluctuations. These temperature changes 
are much more rapid than those shown in Figure 1 , and the effect on the activity of the 
specimens much greater. During the first few days a rise of 7° C. was accompanied 
Figure 3. — Showing record of shell movements of two specimens of 0. lurida and hourly temperature read- 
ings during eight days. Heavy horizontal lines represent records of oysters when open; broken lines indicate 
that shell was closed. A sudden drop in temperature caused the specimens to close, while a rise caused them 
to open 
by an increase of 10 hours per day open; near the end of the test a 7.5° rise produced 
an increase in hours open daily of nearly 10. At the minimum temperature of 6° to 
8° C. the oysters were open only about 6 hours, while at the maximum of slightly over 
15° C. they were open over 23 hours per day, or nearly four times as long. 
