SHORTER ARTICLES AND CORRESPONDENCE 



THE AGE OF SPEED SIRES 



In the May number of the Naturalist, Mr. Redfield makes 

 reply to the criticism of his theory which I made in the issue 

 of January of last year. 



Recalling the interest evidenced by biologists when Mr. Red- 

 field's theory appeared some years ago, and considering that no 



be a proper one for discussion. 



Mr. Redfield 's conception of acquired dynamic development 

 and the data he presented to show its inheritance, strongly sug- 

 gests the direct transmission of effects of use of the organs. 



It is true that more than a majority of successful breeders of 

 trotting horses believe the results of use to be transmitted. A 

 settlement of the question is of no direct interest to horse breed- 

 ing interests. A change of opinion would not change their 

 practise. Selection and environment are the fundamental fac- 



vironment is transmitted. Selectionists would say that the 

 racing test as a feature of environment is an indispensable aid 

 to selection of good individuals and is the only real proof of 

 individual merit. 



The fact that a few breeders who regard training as an aid 

 to selection have been as successful as any of the breeders who 

 think otherwise, goes to show that in the breeding of trotters, 

 practises of best breeders vary but little. They differ in their 

 explanation of how the two factors exert their influence upon the 

 results. This lack of agreement, while of no immediate import in 

 practical breeding, because it bears upon a principle involved 

 is of primary interest in the scientific study of heredity. 



In my contribution last year, I criticized Mr. Redfield \s figures 



development to be proportionate to the amount of racing and 

 to the age. 



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