240 



The Journal of Heredity 



(3) That segregation of factors de- 



termining the grosser differ- 

 ence in spotting occurs. 



(4) That some degree of blending 



occurs, due possibly to minor 

 modifying factors whose ex- 

 pression together with that 

 of the major factor or factors 

 may be obscured by non- 

 genetic variation at present 

 not measured. 



(5) Because of the extreme rarity 



of proven cases of identical 

 twinning in cattle it will 

 probably not be possible to 



measure the amount of this 

 non-genetic variability by the 

 comparison of the spotting 

 patterns of monosexual twins 



The present data cannot be used for 

 measuring the number or the quantitive 

 effects of the factors involved since 

 in the absence of knowledge concerning 

 the genotypes of the animals used, the 

 proportions of offspring of various 

 types can have little significance. There 

 is every indication, however, that an 

 exact interpretation can be arrived at 

 through the collection and study of 

 more data. 



Table 1. Average results of crossing bulls of different spotting grades zvith females of 



all grades 



Sire 



King Model 



(Light, grade 50) 



Dams 



Mean 



Grade Units 



of Black 



Standard \Cocfficicnt 



Dez'iation ,' ^•^, • 

 ( T7„;t,.\ '' ariatton 

 {Units) I , r, ,N 



I (Percent) 



Coefficient of 

 Correlation 

 Dams and 

 Offspring 



46 I 392.39124.91 | 250.50! 17.62 | 63.8416.05 I .611 06 



I I i i I r 

 Off.spring | 50 | 201.00115.41 | 161.50110.89 | 80.3518.24 — =10.16 



II I I Er 



King of the Pontiacs 



Dams 



49 549.49124.38 | 253.00117.24 | 46.0413.74 | .051.10 



I I I ! I r 



(Medium, grade 350) \ Offspring I 49 | 430.10123.32 | 242.00116.49 | 46.2714.90 — = .50 



I II I I Er 



King Pietertje Ormsbv [Dams { 47 | 353.73124.50 I 249.001 17.32 I 70.3916.91 | .341.08 



Picbe I I I I I I r 



(Dark, grade 900) | Offspring | 50 | 638.00123.66 | 248.00116.73 | 38.8712.99 | — = 4.25 



I II 1 I I Er 



All Dams 



142 433. 8U1 14.20 265.00110.61 I 61.0913.23 



Table 2. Results of crosses among Holstein cattle of various grades of spotting. 



