126 CHARLES R. STOCK ARD 



being in the refrigerator for three or four days, they may often 

 resume development at such a fast rate, probably as a result of 

 the stimulation of raising the temperature, that they may hatch 

 only a day or so later than control embryos. The percentage 

 of such eggs that do hatch may also be equally as high as that 

 from the control. 



These statements may be illustrated best by a somewhat de- 

 tailed consideration of the records from experiments. A large 

 number of experiments have been performed and are recorded 

 in my notes, but only a few of these may here be selected as 

 typical examples of the series in general. 



Experiment 905. A group of eggs, 23 hours after fertilization, with 

 high segmentation caps just beginning to flatten on the j'olk-sphere, 

 were carefully selected, being certain that every one was developing, 

 and arranged as follows. 



Lot Ci was placed in the refrigerator at 5°C., C2 at 6°C., C3 at 8°C., 

 C4 at 9°C., and C5 was placed in the top compartment of the refrigerator 

 which ranged from 9.5° to 10°C. 



When 27 hours old, the control group showed the germ-disc somewhat 

 further flattened on the yolk-sphere, but there was no visible indication 

 of a germ-ring and the disc had not begun to descend over the yolk. 

 This expermient was being conducted during the early June season, and 

 normal development at this time was unusually slow. 



At 27 hours old, three other lots were placed in the refrigerator as 

 follows, Di at 5°C., D2 at 6°C., and D3 at 8°C. 



When 48 hours old, the control showed the germ-ring about one-fourth 

 over the yolk-sphere with the embryonic shield clearly forming. The 

 C and D series had become arrested and were still in much the same 

 condition as when placed in the low temperatues on the previous daj'. 



The control at 3 days, or 72 hours old, showed the embryos well 

 formed, though the germ-rings were not yet entirely over the j^olk-sphere 



(fig. 1). 



Lot Ci, having been 49 hours at 5°C., was still in high segmentation 

 stages much the same condition as when placed in the refrigerator 

 (fig. 2). These were now returned to room temperature. 



Lot C2 showed much the same condition as Ci and were also removed 

 from the refrigerator. 



Lot C3 seemed as completely stopped as the other two and was 

 returned to room temperature. 



The members of the C4 group were also in about the same stage as 

 when placed in the refrigerator, though their temperature was 9°C. 

 These remained in the refrigerator. 



The C5 lot in about 10°C. had developed slowly, the caps had flat- 

 tened and the embrj^onic shield had just become visible, though the 



