Gibbs figure of 11 . PC for onset of oviposition in Rhode Island drills 

 coincides with Loosanoff and Davis' figure of 12° C, particularly since the latter 

 worked at temperatures spaced at 3° intervals . Galtsoff et aL 's figure of 

 13 .9° C for the initiation of oviposition in New Jersey is somewhat lcwer thar 

 Stauber's figure of 15° C, but compares favorably with a spawning temperature 

 somewhere between 12 and 15° C in Loosanoff and Davis' data. Adams figure of 

 20" C for oviposition in Canada is noticeably higher than the relatively close figure 

 of 11 1"C for Rhode Island, 12-13°C for England, and 10.9 11.2°C for Long 

 Island Sound, but close to Federighi's figures of 20° C for Virginia and North 

 Carolina . The similarity of response of drills in North Carolina, Virginia, and 

 Canada may reflect the sheltered, shallow, comparatively warm waters in which 

 the Canadian drills normally reproduce. The figures for initiation of oviposition 

 in England, 12-13°C; Rhode Island, 11.1°C; and Long Island Sound, 10.9-11.2°C, 

 are also close. The writer' concurs with Stauber's (pers . com ) suggestion that 

 this similarity indicates that drills originating in the New England area are 

 probably the ones which survived after transportation to England on oysters . It 

 has been shown in the section on distribution in this review that large quantities of 

 live oysters have beer, shipped to Great Britain from the New York area over long 

 periods of time . Similarly it has beer, shown that many of the live oysters shipped 

 to the west coast of North America came from the New York area, and thus probably 

 carried drills from these cool waters to those of the west coast wheie they have beer, 

 able to reproduce. It remains to be demonstrated on a controlled expenmertal 

 basis to what degree drills from warm geographic regions will continue to reproduce 

 when transplanted to cooler regions . 



Some of the data in Table 13, though limited, further suggests that drills 

 may start moving in the spring at a temperature, 4.5"C (Galtsoff et aL, 1937), 

 higher than that, -1 to 2, at which they cease movement in the fall; and may start 

 diillmg and feeding in the spring at a higher temperature, 15° C (Adams 1 1947), 

 than that, 12, 8 "C, at which they cease in the fall The temperatures shown in 

 Table 13 and dates in Table 4 at which oviposition commences in various regions 

 do not necessarily corroborate Stauber s observation that ever in widely separated 

 areas and in the presence of considerable differences in water temperature, spawn- 

 ing of the drill begins within a relatively short period in the spring. 



The low temperatures at which Cole (1942) obtaired maximum locomotion 

 rates in British drills, as compared to the higher temperatures at which Fedenghi 

 (1931c) observed maximum rates in the southern United States, if confirmed, 

 might introduce further support for the existence of physiological races. The rela- 

 tion of minimum salinity tolerarces of drills to drill races is not krown. Nor is 

 n formation available on the function of acclimatization in the evolution of physio- 

 logical races segregated on the basis of response to temperature (Stauber, 1950) 



86 



