574 TRANSMISSION 



he found its descendants highly resistant, flourishing well where 

 ordinary wheat totally failed. It was, apparently, a true mutant, 

 with extra strong resistance to magnesium. 



Influence of development upon prepotency. Many biologists 

 contend that transmission depends to a large extent upon the 

 development of the parent ; that a stallion trotting bred, for ex- 

 ample, would get speed much more successfully if he himself 

 were " developed " or " worked " upon the track than would the 

 same stallion kept equally healthful and vigorous but not devel- 

 oped as to actual speed. A natural conclusion of this contention 

 is, of course, that the same sire will get more speed in his middle 

 and later years than would be possible before he was developed. 



This is the very point of Casper L. Redfield's recent articles 1 

 setting forth what he calls his " dynamic theory of heredity." 

 He brings many instances and much argument in support of the 

 assumption, but in the opinion of the writer the method of proof 

 adopted is not competent to settle the question, nor is any 

 method able to do so that is based upon the simple enumeration 

 of instances. 



As with any other question involving great variability, the 

 only way we can settle this is by employing large numbers on 

 both sides of the proposition ; in other words, by comparing the 

 speed of all the horses gotten by performing sires late in life 

 with the records of the get of the same sires before development, 

 or at least before long service on the track. Even then we must 

 learn what deductions to make, if any, on account of differences 

 in age ; after which, we may hope to learn the real effect of 

 development upon prepotency. 



As the matter stands now, the/^r/ of prepotency is patent to 

 both the casual observer and to the careful student ; but the 

 reasons for this difference in breeding powers are not yet at all 

 well understood. Here, as in many other directions, we await 

 future studies. 



Summary. Individuals of the same ancestry differ marvel- 

 ously in their breeding powers. Some can produce excellence 

 directly in their own descendants, and others indirectly through 



1 See The Horseman, XXV, Nos. 19-41, on " Breeding the Trotter" ; also The 

 American Field, LXII, No. 25, and LXIII, No. 9, on "Evolution of the Setter." 



