No. 595] 



SEX CONTROL IN PIGEONS 



409 



dress before the local chapter of Sigma Xi some 20 months 

 ago. 



The injection of the extracts of gonads, performed 

 now on the third series of birds, has resulted— quite 

 against our wish— in the death of a number of birds. In 

 the main the deaths from ovarian injections were of the 

 more masculine birds ; while the deaths from testicular 

 injections have been among the more, or most, feminine 

 birds. The numbers concerned at present are not large, 

 and a further definite study of the matter will be made 

 before final conclusions are drawn. But the limited data 

 now at hand indicate that the eighth correlation listed 

 on Chart 1 is as it is exhibited there. 



A ninth, and very accurate and convincing kind of in- 

 formation concerning the germs involved in these sex- 

 series has been obtained by means of the bomb calorim- 

 eter. The heat of combustion of some 200 egg-yolks 

 has been determined. One such series of determinations 

 for 1914, in which all available eggs were burned, is 

 shown on Chart 4. It will there be seen that the first 

 clutch of the season bore a higher caloric value than the 

 second, but is otherwise the smallest of the year. Be- 

 ginning with the second clutch laid in June, the succeed- 

 ing clutches to December 1 bear higher and higher heat 

 values. In all clutches too, except the very first, the 

 second eggs show a higher storage of heat units than 

 do the first of the clutch. Here we find the conclusions 

 reached from studies on the weights of yolk, and on yolk 

 analyses, fully confirmed by a study of the burning value 

 of the materials stored. And confirmed by a method in 

 which the error involved in the determination is wholly 

 negligible. The most accurate method, for the study of 

 the storage values of male- and female-producing ova, 

 gives too the results most consistent with the breeding 

 data. 



The tenth and last of these correlations deals with 

 embryological or morphological data. It was found that 

 some females dead at relatively advanced ages showed 

 persistent right ovaries. The right ovary in pigeons 



