F. Pitt 289 



assures me that, though all the cows were white-necked, in some cases 

 very white, the proportion of white-necked calves has been exceedingly 

 small. Again the evidence seems to point to the almost complete 

 dominance of the factor for the extension of pigment. 



Another case is that of a cow named Lady 4th, in which we have 

 an individual apparently heterozygous for the character. She has two 

 or three small spots of white hair on the shoulders. I have records of 

 five of her calves. Judging by their markings these five offspring by 

 normally marked bulls have been two dark-necked dominant homozy- 

 gotes, one heterozygote with just a little white, and two well-marked 

 homozygous recessives. Of course the heterozygotes are the class that 

 one would have expected to be the most numerous, and possibly they 

 are so in reality, for it will be shown presently that it is conceivable 

 that sometimes the expression of the dark-necked factor is inhibited by 

 the presence of another factor. 



A third example is a cow called Playful, almost normally marked, 

 but apparently carrying the factor for the extension of pigment. Three 

 out of her five calves by well-marked bulls have shown no white whatever 

 on the neck, while the two that had a little bore only very small patches. 



This case and that of Lady seem to indicate that the sires with which 

 they were mated likewise carried the factor for the dark neck. The 

 bulls in question were known to be heterozygous for excessive white, 

 and the suggestion is therefore made that the presence of the W factor 

 inhibits the expression of that, which will be hereafter styled D, for 

 dark neck. If this is correct it would explain the production of dark- 

 necked calves by normally marked parents, and the complete and 

 incomplete dominance of the dark neck in other cases. When only the 

 factor for normal colouration is present Z) is a dominant, when that for 

 W occurs it cannot fully express itself How far this conjecture is in 

 accordance with the truth only the collection of much more evidence 

 will show. But the following case supports it — Gaiety, a perfectly 

 marked cow, whose sire and dam were both well marked, had a calf by 

 a bull called Wetmore Laurel, whose markings were typical in all 

 respects, yet their calf was exceedingly dark, without a trace of white 

 on the neck, and was an example of a grade -h 3 animal. It was 

 apparently homozygous for the extension of pigment, so each parent 

 must have borne the factor for this character, the expression of which 

 was inhibited by that for excessive white. This supposition is confirmed 

 when we find that Gaiety's grand-dam was dark-necked. Unfortunately 

 I have not been able to obtain any information concerning the appear- 



