inheritance oe fecundity in domestic eowl.. 313 



Barred Plymouth Rock Matings 



The data will be presented for each gametic constitution 

 separately. The analysis indicates that out of the 9 theoretically 

 possible types of male Barred Rocks shown in table 5 only six 

 have actually ever been used in the breeding pens. These six 

 classes of males represented in the data are classes i, 2, 3, 4, 7 

 and 8. 



In any particular case it is practicable to determine the gam- 

 etic constitution of a male bird in respect to fecundity only 

 through an examination of the records of his daughters. To 

 distinguish different gametic types of males through analysis of 

 the male progeny, while theoretically simply, is practically not 

 feasible while any other investigations are going on. In order 

 to determine the gametic constitution in regard to fecundit}'' of 

 the cockerels from a particular mating it would be necessary to 

 rear to maturity a reasonable number (5 to 10) of these males, 

 and then a year from the time they were hatched to mate each 

 of them with a. number. of females, and rear to maturity and 

 trap-nest for a year a number (3 to' 10 for example) of pullets 

 grown from each of the matings of each of the cockerels. Then 

 from the trap-nest records of these pullets it would be possible 

 to conclude as to what was their grandfather's gametic constitu- 

 tion respecting fecundity. It is evident that relatively enormous 

 experimental resources would be required to carry this out on 

 even a very modest scale. Further the end would scarcely justi- 

 fy the means from either a practical or theoretical standpoint, 

 since the theoretically expected gametic types of males can be 

 readily obtained and their pedigrees will enable one to analyze 

 fully the gametic factors and reactions involved in their prochic- 

 tion. 



Throughout the paper, then, conclusions will be drawn as to 

 gametic constitution of parents from an analysis of the female 

 progeny only. 



The reason why the other three classes of males (5, 6 and 9) 

 are not represented in the matings is to be found in the method 

 of selective breeding practised during the time in which the 

 statistics here analyzed were collected. The chance of using 

 in a breeding pen males of any of these types was small when 

 the selection was carried on in the way that it was. This point 

 will be more fully discussed farther on in the paper. 



