BY RAYMOND PEARL 



The actual course of the average winter egg production (not hitherto 

 published) during the period is given by the figures of Table I and shown 

 graphically in Fig. 1. 



I . 





02-O1 OVO4 0405 

 LATINO YEAR 



05-06 06-07 07-OS 



PIO. 1. 



Diagram showing the course of average winter egg production during 

 the period covered by the mass selection experiment. 



Certainly the first line of evidence, derived from a long-continued 

 experiment, involving more than 2,000 individuals, gives no support to the 

 "statistico-ancestral" theory and indeed is in flat contradiction to one of the 

 most fundamental tenets of that faith. 



Let us next consider the question, 



ARE SOMATICALLY EQUAL VARIATIONS IN FECUNDITY OF 



EQUAL HEREDITARY SIGNIFICANCE? 



In the spring and summer of 1907 were reared 250 pullets, all of which 

 were the daughters of hens that had laid approximately 200 or more eggs in 

 the first year of their life. This group of mothers was reasonably homo- 

 geneous in respect to records of egg production. All had laid about the 

 same number of eggs. Their daughters were, however, far from a homo- 

 geneous lot with respect to egg production. 8 It is plain from the results 

 obtained in that experiment that the egg record of a hen is a most unreliable 

 criterion of the probable number of eggs which her daughters will lay. 

 This is demonstrated by examination of individual cases. Thus consider 

 the two mothers nos. 253 and 14. Their winter production records were 

 nearly identical (65 and 66 eggs, respectively). Their daughters' average 

 winter productions were 23.87 and 2.40 eggs, respectively! Certainly it 

 seems reasonable to conclude that the gametic constitutions involved in the 



8 Full details regarding this experiment have been published as Bull. 166, Me. Ag. 

 Exp. Sta., 1909. See particularly Table I. 



