S i' /'// ^7 (y 



BULLETIN No. 168. 



DATA ON CERTAIN FACTORS INFLUENCING THE 



FERTILITY AND HATCHING OF EGGS.* 



By Raymond Pearl and Frank ^I. Surface. 



In connection with a general investigation of the physiology 

 of reproduction in the domestic fowl in progress at this Station 

 especial attention has been devoted to the study of the factors 

 which influence the hatching of eggs. As a result of the work 

 in this direction which has been carried out during the last two 

 years a considerable mass of data has accumulated. It is the 

 purpose of this paper to present this material and discuss cer- 

 tain definite and positive results to which it leads. 



It should be said at the outstart that this investigation has 

 nothing directly to do with the problems of incubation per sc. 

 This will be clear if we consider briefly the questions with which 

 the present work is concerned. The fundamental, general 

 problem which served as the basis of the investigation may be 

 stated in this way : \Vhat part in the determination of the 

 relative fertility ^ and hatching q;Liality of eggs is played by 

 innate, individual characteristics of the parent birds? If the 

 eggs from a number of different females are handled in the 

 same way and put under identical conditions of incubation it 

 will be found that those from certain individuals will show a 

 much higher percentage of fertile eggs and of hatched chickens 

 than do those from other individuals. Is it not possible to 

 determine some of the factors on which these individual differ- 

 ences depend? The present paper is an attempt in this direc- 

 tion. 



Specifically we have endeavored by the use of appropriate 

 biometric methods, to obtain reliable data on the following 

 questions : 



*Papers from the Biological Laboratory of the Maine Agricultural 

 Hxperimert Station. Xo. 14. 



This paper forms Xo. IV of a series of "Studies on the Physiology 

 of Reproduction in the Domestic Fowl,"' in course of publication from 

 this Laboratory. 



