Yield Mark Transmitted. 71 



mary and permanent ; that of the bull being derived and 

 subordinate. In another part of his remarks, the same 

 writer says: "In young bulls the Yield Mark is dis- 

 tinctly seen at any time after one month old, and impre- 

 cisely the same that it will be when the animal is mature. ' ' 

 If this means that the Yield Mark remains the same in 

 outline form, it is correct; and if it also means that the 

 size of the milk mark, on the bull, is not increased after 

 the age of maturity, it is again correct, as no influence 

 tending to increase or affect the marks of the bull arises ; 

 while the marks of cows continue to increase in size until 

 maturity, and even after, usually, as long as yield increases, 

 which, in some instances, is long after the completion of 

 their general growth. 



In numbers of instances the marks on the bull are but 

 very slight, and become less perceptible, or nearly disap- 

 pear, by the age of maturity ; in such cases organic growth 

 obliterates the faintly inherited marks. The reversed hair 

 mark on the bull does not, then, increase in size, after 

 mature general growth is complete. 



It is established then : ist. That the Yield Marks 

 originate in the cow. 2d. That it is an effect of milk- 

 yield, or its weight-tension. 



It follows that the Yield Mark increases, or remains 

 stationary in size, according to the increased or stationary 

 strain and pressure of milk weight in the udder, and that 

 the same influences that can increase its size must have 

 originated the Yield Mark in milk cows. 



Acquired marks can be transmitted by either sire or 

 dam ; but prepotency, or superior transmissive power, as 

 to the Yield Mark, must be with the cow : ist, because 

 the mark originates in her own organism. 2d, for the rea- 

 son that it enlarges with, and in proportion to, increase of 

 yield ; and 3d, and particularly, from the cows' being /^r- 



