FERTILITY IN ANIMALS 



561 



TABLE LXXIV. GENETIC CONSTITUTIONS OP 

 BARRED PLYMOUTH ROCK MALES FOR 

 FECUNDITY FACTORS 



(a) The Sex Factors. In the fowl the type of sex-inheritance is that 

 designated WZ in Morgan's terminology. Females are heterozygous 

 for the sex-factor; i.e., they are WZ in constitution, whereas males are 

 homozygous, ZZ. W like Y in the XY type is neutral and carries no 

 demonstrable factors. 



(6) A fecundity factor, L, which determines a winter egg production of 

 something less than thirty eggs. It is dominant over the allelomorph 

 /, which is 'present in fowls 

 which produce no eggs 

 during the winter season, 

 but the homozygous con- 

 dition LL does not con- 

 dition a higher winter egg 

 production than does the 

 heterozygous condition LL 



(c) A Sex-linked Fe- 

 cundity Factor, M. Like 

 L it determines alone a 

 winter egg production of 

 something less than thirty 

 eggs. With L, however, 

 it gives a winter egg pro- 

 duction of over thirty. 



Pearl was able to classify the individuals which he used in his ex- 

 periments into classes according to their zygotic constitutions. For the 

 sake of clearness these classes are given in Tables LXXIV, LXXV, 



TABLE LXXV GENETIC CONSTITUTION OF BARRED PLYMOUTH ROCK FEMALES FOR 



FECUNDITY FACTORS 



LXX VI , and LXX VII . These tables represent genetic constitutions which 

 were realized and recognized during the course of the experiments. It 

 will be observed that among the Barred Plymouth Rocks every possible 

 genetic constitution was represented, but among the Cornish Indian 

 Games the factor M was not contained in any individual. 



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