EGG PRODUCTION. 103 



in which a male from a low line was mated with several high producers 

 belonging to a high line and at the same time to several low producers. Of 

 course careful individual pedigi-ees were kept. The offspring of the high 

 producers averaged 49.2 winter eggs against an average of the mothers and 

 their sisters of 52.5 eggs. Nearly all were high producers. On the other 

 hand, the offspring of the poor layers averaged only 11.6 winter eggs. In 

 this experiment high production clearly descended from mothers to 

 daughters. 



In another experiment a male was used that came from a high-producing 

 mother, but on the father's side production was poor. Some of his mates 

 were good producers, some were poor. A few daughters were good laj ers, 

 but most of them, regardless of whether their mother was a high or low 

 producer, were mediocre to poor. In this experiment the influence of the 

 male was more pronounced. 



In other experiments males derived from high lines have been bred to low 

 producers. For example, male B137, a high-line male, was bred to two 

 low birds of low lines. The average winter production of the daughters 

 was high, viz., 54.5 eggs. On the other hand, in the table of the section on 

 inbreeding is shown a case where the production of the offspring of a male 

 belonging to a high line, bred to a high-producing female, viz., No. 8185, 

 of a mediocre line, was relatively poor compared with that obtained from 

 the offspring of females belonging to high Unes. 



In still another experiment a male belonging to a low hne was mated with 

 a female belonging to another low Une. Most of the offspring were high 

 producers. 



These experiments show that we are dealing wdth a situation that is 

 complicated in many ways. It appears, however, to be perfectly clear that 

 both male and female play a part in determining the egg production of 

 their daughters. Whether one is more important than the other depends 

 upon the particular individuals that are mated. In breeding for high 

 production the influence of either must be judged by the production of the 

 offspring. The aim of the breeder should be to produce a line that will give 

 high average production and that will reproduce itseff generation after 

 generation. To this end the contribution of both father and mother must 

 be made. Any male or any female, or a particular combination of a 

 certain male with one or more females that give high production consist- 

 ently, may well be used as breeders as long as they live, or till something 

 better has been secured. 



III. The Exclusion of Par.\sites. 



The investigations on the inheritance of fecundity have led in several 

 unexpected directions. If an analysis of the hereditary basis of fecundity 

 is to be made, it is evident that the problem must be reduced to its simplest 

 form. Disturbances introduced by the surroundings must be avoided. 

 For example, the date at which a pullet lays her first egg influences her 



