54 



INHERITANCE OP CHARACTERISTICS IN DOMESTIC FOWL. 



In table 38 I have given in the section lying between that headed 

 " Father" and that headed " Offspring" the " Matings. " This column differs 

 from the others of the table in not being, in general, based upon observation, 

 but upon a sometimes compUcated judgment. Of course, all of tlie Fj genera- 

 tion, where this generation occurs, may be taken as of DR composition; but 

 the decision as to whether a given individual of Fj is a DR, an extracted 

 dominant, or an extracted recessive is not always easy, because of the mani- 

 festation of imperfect dominance. But the assignments are by no means 

 arbitrary. Taking the Brahma crosses, which are by far the most numerous, 

 we see, from tables 31, B and 33, that those F^ individuals that have a boot 

 of grade 6 or higher are almost certainly extracted recessives (which are 

 equivalent to pure-bred Dark Brahmas) . Those with a grade of 3 or even 4 

 and lower to 2 or even 1 are probably heterozygotes, while those with grade 

 and some of those with grade 1 are extracted dominants. In cases of 

 doubt the distribution of grades in the offspring will give the deciding vote. 

 In case the individual has been used as a parent in more than one mating 

 the results in all the matings are taken into account, for the germinal 

 constitution of an individual must be regarded as fixed at all times and in 

 all matings. The assignment under "Matings" has, then, been made by 

 the application of the above rules. 



In tables 39 to 43 there are grouped together the progeny from matings 

 of the same sort, selecting from table 38 the crosses into which the Dark 

 Brahma enters as the booted parent. 



Table 39. — RR x RR crosses from table S8. 



The significance of the data given in tables 39 to 43 is best brought 

 out by summarizing them. Especially instructive is a comparison of the 

 pure-bred with the hybrids. Since the data are most complete in the case 



