172 CHARLES R. STOCKARD 



eggs were now returned to room temperature, and many of them very 

 soon began again to develop. 



The control at 3 days old showed the embryos well formed, 

 although the germ-ring was not entirely over the yolk-sphere. The Bi 

 lot, after being out of the refrigerator for 24 hours, had high seg- 

 mentation discs which had not begun to flatten down upon the yolk- 

 sphere. There was no indication of the germ-ring or embryonic-shield 

 formation. After 24 hours more the germ-caps had flattened and 

 grown about one-half over the yolk-sphere, the embryonic shield was 

 well formed in most of the specimens and the line of the embryo was 

 visible in the shield. Thus within the first 48 hours after removal 

 from the low temperatures many of these eggs have attained about 

 the same condition as was shown by the present control specimens 

 when 50 hours old. Many of the eggs after refrigeration failed to 

 recover, and died during the first two days at room temperature. 



When 6 days old, the control embryos were twitching and moving 

 their bodies and were in all respects normal in condition. The Bi 

 group contained small embryos without a blood circulation, many of 

 them were abnormal at the head end, and many were short. Thus after 

 developing for 4 days at room temperature they are far behind a usual 

 four-day embryo. 



The Bi group were carefully surveyed for deformities when 9 days 

 old. Four eggs had yolk-sacs containing blood-cells and chromato- 

 phores, but without formed embryos. Six eggs still had an early cell 

 mass at the upper pole which had not developed, although even at 9 

 days it was translucent and alive. There were 10 deformed embryos 

 without a circulation, and 4 deformed but with a circulation. The 

 majority, 45, of all living specimens seemed normal, with vigorous 

 circulations. Thus more than 34 per cent of the specimens which 

 survived the low temperature were grossly abnormal. Three of the 10 

 eggs which contained abnormal specimens with circulating blood 

 showed double embryos. One was two-headed, and two were double 

 throughout their anterior halves, each having two heads and two 

 bodies with a single caudal half. 



The control embryos were with two exceptions all fine normal speci- 

 mens. Two of the 86 individuals were small and considerably behind 

 the others in their stage of development, although their structures 

 were normal and they later succeeded in hatching several days after 

 their fellows. 



This experiment again shows a pronounced difference between 

 the modes of development in the normal control lot of eggs and 

 in a similar lot which had been inhibited by lowering their tem- 

 perature before the time of gastrulation. More than 4 per cent 

 of the eggs which survived the inhibition contained double 

 embryos, and one-eighth of all the gross abnormalities was of this 



