464 GENETICS IN RELATION TO AGRICULTURE 



the horned condition; so that, given a polled individual, it is the simplest 

 kind of a Mendelian problem to establish a race all the individuals of 

 which are polled. 



From the more strictly economic side there is very slight evidence of 

 the occurrence under observation of any definite mutation. Arenander 

 reported some results with milk cows which might indicate mutation. 

 The evidence deals with a cow Ortvart and her progeny. This cow 

 gave milk of an abnormally low fat content, and she transmitted this 

 character to her daughters. But nothing definite is known as to the 

 parentage of Ortvart. Furthermore she was as strikingly distinct in 

 color characters as in low fat content of the milk; she was white with 

 black ears and small spots. Of her seven daughters five are described 

 as of the same color and pattern, the remaining two were of the same 

 pattern but the ears and spots were red. There is no acceptable evidence 

 of mutation in this case, but the evidence of inheritance of the trait of 

 prodticing milk of low fat content is unmistakable. So also Pearl's 

 case of a mutant in egg production is, probably, as he himself states, 

 merely a case of extreme Mendelian segregation. The data for this 

 case are given in Chapter XXXI. We may conclude, therefore, and 

 rightly, that any system of herd improvement founded on the search 

 for and utilization of mutants is doomed from the beginning to failure, 

 for mutants of a beneficial character appear so rarely as to have almost 

 no practical significance. If by some fortunate chance a breeder should 

 find himself in possession of a favorable mutant individual, however, 

 it is a simple problem in Mendelism to establish its characters in a 

 constant race. 



