TllH INHERITANCE OF THE MLZZEE C.OLOll! 



359 



in cases of incomplete epistacy. These bulls are probably homozygotes 

 as regards the P-colour, as only P-coloured muzzles appear in crosses 

 with P-cows. However, no /v-calves would appear in this case in 

 crosses between these bulls and M-cows constituted ggppPiPi or 

 ggPppiPi. The bulls in question must then be heterozygotes, or the 

 genotypic constitution of the il/-cows must be another, for instance 

 GgPPPiPx. The same is true of the cross P-bull X A^-cow. No 

 7v-calves would appear if /v-cows from P X P-animals were crossed 

 with a homozygote P-bull. However, not one of the cows nos. 747, 

 805, 807, 808, 821 and 868 descends from P X ^-animals. They may 

 then have given 7v-calves with a homozygote P-bull. The descent of 

 the 7v-cows crossed with the P-bull no. 100 is not known with regard 

 to the colour of the muzzle. 



It is shown in table I that out of 317 calves 53 got mixed and 

 13 flesh coloured muzzles, while the parents had wholly pigmented 

 ones. The parents of the 66 calves are heterozygotes. The J^-parents 

 must have the constitution ggPpPtpi according to the tables given. The 

 Ç-parents of the /v-calves also belong to this genotype, while the 

 Ç-parents of the il/-calves, with the exception of those giving rise to 

 7v-calves as well as i¥-calves (see table XHI), may belong to either of 

 the following genotypes: ggppPiP\, ggPPpipi, ggPPPip\, ggPpPiPx 

 and ggPpPiPi. However, ist appears probable that also the 2-parents 

 of the M-calves belong to the genotype ggPpPxpx as the numerical 

 relation 53 mixed : 13 flesh coloured entirely corresponds to the rela- 

 tion 4 mixed : 1 flesh coloured to be expected in the cross ggPpPxpx 

 X ggPpP\Pi according to the following scheme: 



If crosses had been made between P-animals belonging ex- 

 clusively to the genotype ggPpPxPx, the number of wholly pigmented 

 calves would have been 11 times greater than the number of flesh 



