TRANSMISSION OF MODIFICATIONS 409 



3. So much of this exercise, or development, as contributes 

 simply to constitutional vigor and good health will have its effect 

 under quite another principle. Moderate exercise over against 

 absolute inactivity should show some results, but this is entirely 

 outside the present inquiry. What we desire to know is whether 

 the extreme development of a faculty in an individual will aug- 

 ment its transmission above what would otherwise have been the 

 transmitting power of that individual. 



Mr. Redfield's conclusion that this transmission is limited to 

 the same sex that the development of a sire affects only his 

 male offspring does not rest upon good grounds, and is against 

 what is generally known as to sex transmission. It will be seen 

 later that sires are slightly but not noticeably prepotent over 

 dams in male offspring, and vice versa ; but the difference is 

 slight, and not marked, so far as it has yet been studied by the 

 statistical method, which is the only reliable one for the deter- 

 mination of questions of this character. 



Effect of development upon the transmission of milking quality. 

 It is a widespread belief that a heifer will make a better cow if 

 brought into milk at two years of age than she will make if her 

 milking powers are not developed till later. Will her later 

 calves, dropped say at six years of age, be influenced by the fact 

 that she was a cow at two years of age rather than not until four 

 or five ? The question cannot be answered at present, though 

 records are accumulating which will almost certainly afford an 

 answer in the near future. In the meantime it is both fruitless 

 and hazardous to speculate. We must turn in another direction 

 for the only known evidence that is valuable, and reason by 

 inference from the behavior of characters under degeneration. 



SECTION VIII EVIDENCE FROM DISAPPEARING 

 ORGANS 



It seems to be true in general that when a part once useful is 

 no longer used, its doom is sealed. It at once begins to degen- 

 erate and its final disappearance seems only a question of time. 

 In this way the snake has lost all its limbs ; * the whale, its hind 

 1 The python still has rudiments of the pelvic bones. 



