THE ASSOCIATION OF CHARACTERS 309 



better is the chance that their seeds will be of superior qual- 

 ity. Selection of seed-bearers based on a direct measure- 

 ment of their average progeny, as it was originally appUed 

 by Vilmorin, seems at the present time to be too troublesome 

 for practice, though theoretically it would be much less open 

 to criticism, and though in the long run it would also yield 

 better practical results. 



Such are the laws, which govern that most comphcated 

 phenomenon of the correlated dependency of characters and 

 qualities on the outer conditions of Hfe. 



E. UNIT-CHARACTERS 



The mechanism of an organism consists of numerous 

 parts which are more or less exactly fitted to one another. 

 Nearly all of them are dependent on some others in their 

 development, some profiting by the preponderance of these 

 and others being restricted thereby. Moreover they are 

 governed by the outer conditions of hfe and these influences 

 change some of them in the same direction and others in an 

 opposite one. Thus we come to the conception of a general 

 interdependency of all parts, organs, and quahties of an 

 organism. They are governed more or less by the same 

 laws which cause them to undergo corresponcUng changes 

 when subjected to the same influences. 



In practice, this interdependency permits the indication 

 of valuable quahties by purely botanical marks, and gives 

 the possibihty of basing selection upon marks which may 

 be controUed in thousands of individuals without sacrificing 

 them and without the need of testing all of them directly by 

 their economic value. It is an important principle in plant- 

 breeding, which makes the work more rehable and more 

 available to horticulturists and agriculturists in general. Our 

 great admiration for men of genius may not prevent us from 

 deploring that the improving of our domestic animals and 



