44 FECUNDITY IN THE DOMESTIC FOWL 



the year of over 200 eggs. She was mated and produced plenty of eggs 

 during the hatching season, but they hatched very badly. Only one 

 female worth putting in the house was obtained. This pullet (E356) made 

 a winter record of only 39 eggs, just about the general flock average. E356 

 was not mated. Her mother (D352) was kept over and bred to another 

 male the next year, in the hope that as a fowl she might produce more and 

 better chickens than she had as a pullet. As a matter of fact she was again 

 able to produce during the whole breeding season only one pullet worth 

 putting into the laying house. This pullet (F163) made a winter record of 

 but 11 eggs. F163 was bred in 1910, but produced only one daughter 

 worth saving. This daughter, G429, has made a winter record of 18 eggs. 

 It would be hard to get clearer evidence than that afforded by this breeding 

 history that D352 belonged to a low fecundity genotype, in spite of her 

 individual high laying record. 



THE EFFECT OF THE SELECTION OF FECUNDITY GENOTYPES 

 Let us now consider the bearing of the results so far set forth on the 

 problem of selection. Taking first the question of the effect of selection for 

 fecundity within a population, it is plain that if different degrees of fecundity 

 have a genotypic basis, as the facts above presented and a considerable 

 mass of data of a similar kind, which owing to lack of space can not be 

 given here would appear to indicate, then the results following selection 

 will depend entirely upon the genotypic constitution of the population. 

 If high fecundity genotypes are present they can be isolated by selection. 

 If they are not present selection of high laying hens will not change the 

 average production of the flock. 



The aim of the selection experiments since 1907 has been to discover 

 and propagate separately genotypes of high fecundity and genotypes of low 

 fecundity, all the birds being taken from the same general flock. The 

 results of this work are shown in the following table and in Fig. 5. This 

 table is to be regarded as a continuation of that given on p. 327, supra, 

 which shows the results of mass selection for high fecundity in the same 

 stock. 



EFFECT OF SELECTION FOR FECUNDITY WITHIN THE POPULATION 



1907-08. Mean winter production of general population 15.92 



1908-09. Mean winter production of all high fecundity lines 54. 1 6 



1908-09. Mean winter production of all low fecundity lines 22.06 



1909-10. Mean winter production of all high fecundity lines 47-57 



1909-10. Mean winter production of all low fecundity lines 25.05 



1910-1 1. Mean winter production of all high fecundity lines. 5-58 



1910-1 1. Mean winter production of all low fecundity lines 17.00 



