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THE AMERICAN NATURALIST [Vol. XLIII 



in former years the export was considerably greater than it is 

 Waldemar Jochelson. 1 



AGE OF TROTTING HORSE SIRES 

 Theories of heredity deduced from statistics always require 

 critical examination. Statistics of heredity, like those of other 

 subjects, offer striking possibilities to searchers for support of 

 preconceived theories. I have recently completed some work 

 with the trotting horse records, the result of which may be of 

 interest inasmuch as it does not corroborate the results of other 

 work in the same field. 



Mr. C. L. Redfield has recently published a dynamic theory 

 of development based largely on the statistics of the age of 

 sires of average and of preeminent trotting horses. He as- 

 sumes that by exercise a horse acquires "dynamic development," 

 which facilitates speed and is transmitted. Dynamic develop- 

 ment will naturally be greater in old than in young horses; in 

 horses that are campaigned than in those not prepared for 

 racing. Other things being equal, an old stallions' colts would 

 inherit greater dynamic development and be faster than other 

 colts sired by the same horse while younger. He found that the 

 average trotting-bred horses, represented by the first one thou- 

 sand animals listed in the Index Digest, were sired by stallions 

 at an average age of 9.43 years. Representing the superior 

 trotting horses by the 2.10 list, he based his calculations on the 

 males appearing in four generations of each pedigree. The 

 average time between generations in the male line in this in- 

 stance was found to be 14 years ; the sires were therefore prac- 

 tically 13 years old at the time of service. The difference be- 

 tween 9.43 and 13 years as the ages of sires of average and 2.10 

 horses is a very striking one and forms the basis of argument 

 for the transmission of the dynamic development attributable 

 to advanced age. 



The matter of inheritance of dynamic development produced 

 by racing, I propose to discuss at another time. 



1 Leader of the Kiabouschinsky Expedition to Kamchatka, the Aleutian, 

 Komandorski and Kurile Islands. Organized by the Imperial Kussian Geo- 

 graphical Society. From 1900 connected with the Jesup North Pacific 

 expeditions of the American Museum of Natural History. This contribu- 

 tion will be of very great interest both to ethnologists and zoologists.— 

 H. F. O. 



