96 
BULLETIN OF THE BUREAU OF FISHERIES 
TEMPERATURE EFFECTS 
Early in the study of the oyster drill it became evident that temperature had a 
great influence on its activities. During the winter months the animal becomes 
inactive, remaining attached to the substratum or lying passively on the bottom. 
A temporary rise in temperature causes slight creeping, but no feeding. 
During the winter of 1926-27 about 100 animals were kept in the laboratory 
tanks and their activities studied in relation to the daily water temperature. Through- 
out the greater part of December and January they remained totally inactive; in 
February they showed slight sporadic movements. They crept up the sides of' the 
tank— a reaction which always followed the beginning of activity. Toward the end 
of February and the early part of March unusually low temperatures occurred, 
bringing about complete immobility. On March 14, although the temperature rose 
above 10° C. the salinity was low so that they showed no movement. Inactivity 
obtained during the latter part of March and early part of April. From the middle 
of April until early May the animals were inactive because of a combination of low 
temperature and low salinity; then they became more and more active. These 
observations were corroborated by those obtained at Beaufort, where temperatures 
below 10° C. caused immobility. 
Temperature affects not only the general activities of the animal but also feeding 
and spawning. At Hampton Roads during 1927 spawning first occurred in the 
laboratory on May 19. On May 20 the first egg cases were collected in the field. 
In Beaufort (1928) the first spawning occurred on March 31. In both cases the water 
temperature had risen over 20° C. for some time. 
Feeding is greatly affected by temperature. At Hampton Roads the drills 
began to feed during the latter part of March (1927) when the temperature rose 
above 15° C. On March 23 the temperature fell to 10° C. and feeding immediately 
stopped, a reaction not due to salinity because on these dates the salinity was over 
15.00 parts per mille. (Fig. 4.) . Some feeding occurred during the middle of April, 
and from May 2 (17.5° C.) it continued throughout the summer. During these 
observations it was also noticed that drilling would be completely halted by a sudden 
