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CARNEGIE INSTITUTION OF WASHINGTON. 



Table 2. — Summary of data from experiments with altered oxygen pressures and low 



temperatures. 



tained from the treated eggs. The data obtained from the subjection of 

 embryos to low temperatures are in most respects similar to those obtained 

 from reduced oxygen pressures, but the resulting sex-ratio certainly departs 

 less from the normal and fewer and less significant numbers are available. 

 Since embryos of known sex were killed in only about half of the experiments, 

 it is statistically more correct to calculate percentages for 'killed' and 'sur- 

 vivors' upon the numbers of males and females found in these experiments 

 alone. This calculation is supplied in table 3, where the order or nature of 

 none of the comparisons made above is changed by the second method of 

 calculation. 



"These experiments, therefore, afford some evidence (hitherto entirely 

 lacking) that a metabolic sexual difference characterizes male and female 

 dove embryos. And the resulting metabolic difference here indicated for 

 the embryos is in complete accord with the metabolic difference which our 

 previous work with pigeons has shown to characterize the ova and the adults." 



Table 3. — Summary excluding experiments in which no "sexed" embryos were killed. 



Control of the Sex-Ratio. 



Very significant departures from the typical 50-50 sex ratio are 

 frequently found, and more rarely the extreme case of 100-0 appears 

 either in nature or in experiments conducted in the laboratory. When 



