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THE AMERICAN NATURALIST [Vol. XLIV 



Mr. Redfield's own words will explain the evidence from 

 which he argues for the value of age : 



I said that I took one thousand registered stallions, alphabetically, 

 from the " Index Digest " of the " Register," and calculated the ages of 

 their sires at the time when these registered stallions were foaled. From 

 these I determined that the average time between generations in the 

 male line was 10.43 years, which would give the average age of sires as 

 9.43 years at the time of service. I then said that, making all reason- 

 able allowances for errors, the average time between generations in the 



period might be used as a standard in testing the age part of the theory. 

 So far no one claims to have tested the accuracy of my calculation; no 

 one claims that the figures I gave were wrong; and no one has said 

 that these figures can not properly be used as a standard; yet if I 

 am to be controverted, one of the first things to be done is to dispute 

 the accuracy of my standard. 



animals to be used in testing the inheritance of dynamic development, 

 and I calculated the ages of their male progenitors for four generations. 

 The number of animals involved was over five thousand and I gave the 

 average time between generations in the male line for the production 

 of 2.10 trotters as being approximately 14.00 years. This is an 



from the « Register," and my explanation of this remarkable difference 



So far no one has disputed the accuracy of my computation and no one 

 has attempted to give any other explanation of such an unusual 



My objection was to comparing the average age of immediate 

 sires in one case with that of all sires in four generations in the 

 other case. I showed that when we take only immediate sires 

 in both cases, it is shown that the average age of the sires of 2.10 

 horses is practically the same as that of a vera ire horses as given 

 by Mr. Redfield. 



He now shows that in the case of the 2.10 trotters, while their 

 sires were of an average age of 10.4 years, their grandsires 

 averaged 12.5 years, the great-grandsires 13.5 years, the great- 

 great-grands ires 14.5 years; the stallions appearing in the next 

 two lines at the ages of 15 and 15.98 years. 



The evident conclusion from this statement is that our best 

 horses have come from an increasing popularity of younger sires. 



But this statement regarding the age of sires in various lines 



