

TRANSMISSION OF MODIFICATIONS 407 



may do his own thinking, some of the principal references relat- 

 ing in part to use and disuse are given in the footnote. 1 



It is important that we know the truth in this matter if pos- 

 sible. If the perfection of development that comes only with 

 use is to any extent transmitted, then we must put our speed 

 horses through a long course of training and develop them fully 

 before we may hope that they will transmit maximum speed. 

 If this theory be correct, then the heifers from a mature cow 

 that has been long in milk and made record, will be capable 

 of developing into better milkers than would be possible if 

 the dam had never made extreme records, or than would be 

 possible with the earlier calves from the same cow (before the 

 extreme records were made). Manifestly the age of the bull 

 will not count, as he is incapable of developing this particular 

 character. All he can do is to transmit, unaugmented and 

 unchanged, the hereditary faculties of milk production exactly as 

 they descended to him. In meat production of course, as in speed, 

 the case would be different, as both sexes may be conceived as 

 capable of adding to (?) or detracting from (?) the racial intensity 

 by reason of their own development or lack of development. 



This subject is now under investigation, and while the point 

 would seem to be easy of determination, yet it involves the care- 

 ful study of all the progeny of many individuals both before and 

 after development. On this point, however, evidence may be 

 expected at no very distant date. 



Effect of development upon transmission of speed in horses. 

 In a recent series of articles, 2 Casper L. Redfield takes the 

 position that the effects of speed development are transmitted, 

 and he cites numerous instances calculated to show that maxi- 

 mum speed is transmitted only from sires with long and 



1 Against transmission : Weismann, Germ Plasm, pp. 392-410. In favor of 

 transmission : Romanes, Darwin and After Darwin, II, 60-287 ; Cope, Origin of 

 the Fittest, pp. 194-203, 405-421, and Primary Factors of Organic Evolution, 

 pp. 246-384; Eimer, Organic Evolution, pp. 153-173, 205-221. Non-Partisan: 

 Lloyd Morgan, Habit and Instinct, pp. 280-322 ; Vernon, Variation in Animals 

 and Plants, pp. 352-370. 



2 Mr. Redfield's theories are best set forth in a series of articles entitled " Evo- 

 lution of the Setter," in American Field, LXII, Nos. 25-27, and LXIII, Nos. 1-9. 

 They are further set forth in a series entitled, " Breeding the Trotter," published 

 in The Horseman, XXV, Nos. 19-34. 



