BREEDING POULTRY FOR EGG PRODUCTION. 163 



other led tq the production of six adult daughters, all of which 

 are relatively high layers, with the single exception of G495, 

 which has a record of only one egg, and that record is doubt- 

 ful. This bird has probably never laid an egg, and almost cer- 

 tainly is pathological. 



Leaving this bird out of account because pathological, the 

 mean winter production of the family is 52.8 eggs, very strik- 

 ingly different from the average (9.67 eggs) of the birds of the 

 same generation in the main low line in which the mutation 

 appeared. 



Two other daughters of the mutant E248 were mated to 

 $ D3 1 , a bird known not only to belong to a genotype of mediocre 

 to low fecundity, but to be remarkably prepotent in respect to 

 this character, so that practically regardless of the females with 

 which he has been mated the get has been uniformly poor in 

 respect to egg production. Four adult females resulted from 

 the two matings under discussion. They have an average win- 

 ter production of 23.75 ^ggs- There are several possible ex- 

 planations of this result, but the most probable is that we have 

 here simply one more instance of the extraordinary prepotency 

 of ^ D31. 



The last of the daughters of the mutant was mated to a 

 cross-bred male, No. 578, and consequently the progeny can not 

 fairly be compared with the pure Barred Rocks in respect to 

 fecundity. 



The facts here briefly discussed are shown in the following 

 table and graphically in Fig. 83. 



It is apparent from the table and the diagram that the main 

 line and the "mutant" line are entirely distinct. Indeed they 

 do not overlap in their ranges even excepting only the pathologi- 

 cal individual G495. The "mutant" pullet E248, for some rea- 

 son or other, possessed the capacity both to lay a relatively large 

 number of eggs, and the genes necessary to make this quality 

 appear in her progeny. Whether this individual is to be regard- 

 ed as a true "mutation" would appear to be largely a question 

 of definition. In the writer's opinion the most probable ex- 

 planation is that E248 is a Mendelian segregation product. That 

 is, let it be supposed that both D168 and D61 were heterozygous 

 with respect to degree of fecundity, and were producing in some 

 (unknown) ratio both "high fecundity" and "low fecundity" 



