TRANSMISSION OF MODIFICATIONS 363 



mind. It is not whether an individual with strong tendencies is 

 a better breeder than one with weaker tendencies, that is 

 conceded; it is not whether a race living under a favorable 

 environment flourishes better than one living under hard con- 

 ditions, that is conceded, too, for natural selection is inevi- 

 table ; but the question is, whether the individual will be the 

 better or the worse as a breeder because of the special develop- 

 ment he has acquired. 



The answer to this will decide the question whether we shall 

 keep our meat-breeding animals in high or in moderate flesh ; 

 whether we must develop the speed of our racing stallions and 

 mares ; whether a given sire or dam is a better breeder after 

 speed is developed than was the same individual when green. 

 It will determine the whole matter of the importance of develop- 

 ing breeding stock, not only as a means of increasing natural 

 capacity, but as a means of intensifying the powers of trans- 

 mission. 



Fortunately we are not without facts bearing upon this 

 vexed question ; but the whole field is exceedingly difficult, and 

 reliable evidence is eagerly sought. It is the more difficult to 

 secure because of the ever-present and always powerful influence 

 of selection. 



The particular modifications (acquired characters) that have 

 been most discussed and whose transmissibility has been advo- 

 cated on the one hand or denied upon the other are of four 

 distinct kinds : 



1. Mutilations due to injury or destruction of racial characters 

 after they have reached full development. 



2. Habits of life arising out of the exigencies of existence. 



3. Structural peculiarities due to use and disuse. 



4. Adaptations to climatic conditions. 



These are commonly all considered as acquisitions in the 

 sense of additions to racial characteristics. In the view advo- 

 cated by the writer they are all reducible either to different 

 degrees of development of racial characters, or to the uses to 

 which these are put under the conditions and exigencies of 

 life. They will be considered in the order named, always with 

 the question uppermost in mind, Are they transmissible ? 



