F. Pitt 285 



(29544). This was also a very fine typical animal, well marked, and 

 most fashionably bred, yet evidently heterozygous for too much white. 

 When mated with six cows of normal appearance but believed to carry 

 the factor for white he sired 18 calves, of which 13 were well marked 

 and 5 badly. Taking into consideration the smallness of the numbers, 

 when the transposition of a unit will effect the agreement with 

 expectation, this again is a fair approach to the 8 : 1 ratio. His matings 

 with 13 cows homozygous for normal markings resulted in 39 typically 

 marked calves in accordance with expectation. Theoretically half of 

 these should be heterozygotes, but so far too few have been bred from 

 to afford any evidence as to what proportion of them bear the factor for 

 excessive white. Lastly Bounds Chance has had from four badly marked 

 cows, presumably pure recessives, 16 offspring, 9 being too white, and 7 

 properly marked — expectation 8:8. 



The produce of the above bulls may be set forth as follows : 



NN or NW WW 



Lowland Paradigm NW x 5 cows NW= 12 : 5 

 Bounds Chance NW x 6 cows NW= 13 : 5 



Expectation ... : 8 : 8 



Recessive Nature of the White Factor Illitstrated by a Pedigree: 

 Diagram 1 is a pedigree, traced through six generations, which illus- 

 trates in another manner the way in which excessive white crops up 

 among normally marked cattle. The family shown has produced six 

 individuals marked with too much white. The pedigree enables one to 

 see at a glance, what has already been set out in the previous tables, 

 that excessive white is due to a simple Mendelian factor acting as a 

 recessive to that for normal colouration. The futility of the ordinary 

 methods of elimination is also apparent. It must be added that the 

 genetic constitution of the cattle shown in this pedigree is deduced 

 from their entire produce, which of course are too many to be shovm 

 completely in the diagram. 



