December 16, 1910] 



SCIENCE 



871 



scribed the results in the F, generation of 

 crossing reciprocally Barred Plymouth Kock 

 and Cornish Indian Game fowls. In these 

 papers it was shown that the type of barred 

 pattern seen in Barred Plymouth Eocks ap- 

 peared to be inherited in a sex-limited man- 

 ner, the females of the breed mentioned being 

 heterozygous in respect to the factors de- 

 termining both sex and the barred pattern. 

 These experiments have been continued and 

 it is our purpose in this paper to present the 

 evidence obtained in the F^ generation, which 

 is in complete accord with the hypothesis of 

 sex-limited inheritance adduced to account 

 for the F^ results. In this paper the inheri- 

 tance of the barred pattern in these crosses 

 ■wiU be alone discussed. In a later paper other 

 characters, including fecundity, shank color, 

 etc., will be considered. 



At the outstart it should be recalled that 

 in the F^ generation of this cross, but one 

 type of non-barred birds appeared. These 

 ■were the females resulting from the cross 

 C.I.G. c? X B.P.E. S. These were solid black 

 birds. In the F, generation three main types 

 of non-harred birds appeared. These were: 

 (a) solid black birds, like those in F^, (h) 

 solid white birds, and (c) birds showing the 

 game pattern and type of coloration. In the 

 present discussion all of these birds wOl be 

 considered together, as non-barred, i. e., lack- 

 ing the barred pattern. While they are dif- 

 ferent among themselves they are alike in this 

 point: they lack the barred pattern. The 

 analysis of these different types of non-barred 

 birds will be considered in detail in a later 

 paper. 



Confining our attention here then to the 

 two main categories of birds with, and birds 

 without, the barred pattern, we have the re- 

 sults set forth below. It will be noted that' all 

 possible matings of the F, crosses inter se 

 and with the parent birds, were made in the 

 experiments. 



Using the following symbols, 



B = presence of the barred pattern, 

 6 ^absence of the barred pattern, 

 F ^ presence of the $ sex, 

 / = presence of the cJ sex, 



we have the following constitutions of the 

 birds used, the assumption being made that 

 both B and F can not exist together in the 

 same gamete: 



Pure Barred Rock cJ==^Bf . Bf, 

 Pure Barred Rock ? =^Bf . bF, 

 Pure Cornish Indian J^bf . bf, 

 Pure Cornish Indian J := 6/ • bF. 



This leads to the following expectation in 

 the 



jPi Generation: 



Mating: B.P.R. ^ X C.I.O. $. 

 Expectation : 



Bf .BfXbf ■ bF = Bf . bf = Barred ^J, 

 + Bf . 6ii' = Barred $?■ 

 Mating: C.I.G. ^ X B.P.R. % 

 Expectation : 



bf . bf y. Bf ■ bF = bf . Bf = Barred SiS, 



+ bf .bF=i Non-barred $2- 



It was shown in the papers already referred 

 to that these expectations were realized ex- 

 perimentally in the F^ generation. 



We come now to the 



F, Generation. 



I. Mating: Pure B.P.R. (^ X 1<\ Barred Cross- 

 bred' $. 



Expectation ; 



Bf . Bf Xbf .bF = Bf .bf = Barred S^, 

 + Bf .bF = Barred ??. 



' After careful consideration it has seemed to 

 the writers advisable to use the term " cross-bred " 

 to designate the offspring from crosses of different 

 breeds of poultry, instead of the term " hybrid." 

 reserving the latter to designate the progeny of 

 species crosses. This was the usual connotation 

 of tlie word " hybrid " before the rediscovery of 

 Mendel's laws. While " hybrid " has the sanction 

 of " good biological usage " at the present time 

 as applied to all sorts of crosses, it seems desirable 

 in the interests of precision of diction in scientific 

 work to use different terms for the progeny from 

 crosses of closely related and more distantly re- 

 lated forms. " Cross-bred " is a term of unmis- 

 takable meaning and has long been employed by 

 breeders of domestic animals with the sense in 

 which it is Iiere used. It is unfortunate that we 

 do not have in English in a single word a polite 

 equivalent of the German " Bastard " for use in 

 such cases. 



