130 CHARLES R. STOCKARD 



heart beat, but had not estabhshed a circulation and others had not 

 yet developed a heart beat. 



Lot C2 showed a good circulation in almost all. 



Lot C3 presented a majority with good circulation, there were, how- 

 ever, many with imperfect circulation or no circulation, although the 

 heart was pulsating. 



When 9 days old, the control presented a perfectly normal condition. 



Lot Ci showed practicalh' every specimen normal and strong, 

 apparently just as good as the control, though somewhat behind. 



Lot Co were in equally as good a condition. 



Lot C3 was much the same as the other two groups. 



Lot C4 also seemed to contain all normal embryos. 



Lot C5 were further advanced than C4, since they had continued to 

 develop slowly while in the refrigerator at the higher temperature of 

 about 10°C. They had, therefore, developed slowly for 4 days, and 

 after having been out for 4 days were practically perfect in their 

 development. 



Lot Di were all normal at 9 days old and as perfect as the control 

 except for the fact of being behind in developmental time due to the 

 few days stand-still spent in the refrigerator. Thus development 

 can be discontinued for 3, 4, or 5 days at the stages used in this 

 experiment (27 hours old, just after gastrulation has started) with no 

 subsequent ill effects on the development and structure of the earlj^ 

 embryos. 



Lot D2 contained specimens further behind in development than the 

 Di group, since they remained in the cold longer, but all appeared 

 perfectly normal at this tune. 



Lot D3 were all normal. 



At 12 days old, the control seemed about in the condition to hatch. 



The C series which had been subjected to developmental interrup- 

 tions after being 23 hours old now presented perfectly normal con- 

 ditions. In lot Ci three specimens had not developed and sixty were 

 normal This is as good a record as is usually found under ordinary 

 conditions. Lot Co contained about 100 specunens, which were all liv- 

 ing and nornial. Lot C3 had about the same number in similar con- 

 ditions. Lot C4 also contained about 100 normal specimens, so that the 

 numbers examined were sufficienth' large to furnish a very reliable 

 index of the reactions. 



Lot C5 contained a few more than 100 normal specimens and a 

 single individual that was abnormally small, yet even this one was 

 sufficientl}^ normal to have a free blood circulation. 



Lot Di, which was put in the refrigerator 27 hours after fertiliza- 

 tion, contained six specimens that did not develop out of a total of 

 seventy-five eggs. The other sixty-nine specimens were normal. The 

 D2 lot were all normal, and so was the D3 group, yet all were behind the 

 control in their developmental stage corresponding to about the 

 length of time they had spent in the refrigerator. 



