4 
BULLETIN OF THE BUREAU OF FISHERIES 
was begun during the relatively warm weather of October and continued until Novem- 
ber 22, when the temperature of the water had fallen to about 5° C., or hibernating 
temperature, according to Galtsoff. 2 After about the first week when the specimens 
were not open as much as expected, it will be observed that the curves of shell activity 
and average temperature are suggestively parallel. Beginning at about November 1, 
when* the temperature was about 10° to 11° C., and the specimens were open some- 
thing over 20 hours daily, there is a progressive decline until at the end the tempera- 
ture is only 5° C. and the specimens open only about 15 hours daily. Roughly, then, 
for with only two specimens considered in this manner a precise statement can not 
be made, a drop in average daily temperature of 5° C. over about 20 days was accom- 
DECEMBER 
JAN. 
Figure 2. — Showing the parallel between the number of hours open daily of six 
specimens (0. lurida) and the average daily temperature. Records for three 
days were lost 
panied by a lowering in hours open daily of about 5, or 25 per cent. These same 
results are calculated below in a different manner. 
At best the above conclusion is only suggestive, but it is important in at least one 
respect, namely, that at the hibernating temperature (6° C.) during the last three 
days the oysters were not- continually closed. 
Another series (8 and 9, Table 1) shows more strikingly this relationship between 
shell activity and temperature. In this experiment one kymograph sheet was unfor- 
tunately lost, and there is a break in the records. (Fig. 2.) During part of the time 
the inflowing water was slightly heated by passing it through a lead coil which was 
immersed in heated water. This heating equipment was just being installed and did 
not work satisfactorily at first, so there are periods during which the water was heated 
and other periods when the temperature was low. The curves of temperature and 
3 Unpublished manuscript in the files of the Bureau of Fisheries. 
