58 MARRIAGE AND DISEASE. 



and give tone or bent to the whole. Of the innumer- 

 able characters inherited by the child, some are recently 

 acquired by the family, and are but slightly developed 

 and still more slightly fixed; others, even of long 

 standing, are fading from want of cultivation, or from 

 some change in the environment ; while others, again, 

 are prominent or strongly marked, not from long 

 descent alone, but from this coupled with continued 

 cultivation, i.e., by intermarriage among persons of 

 the same variety in an environment favourable to the 

 continuance of the character. In fact, prepotency is 

 another name for fixity, and fixity of a character is 

 only to be secured by repeated transmission; which, 

 in turn, is only to be gained by " in and in " breeding 

 in as nearly constant an environment as is attainable. 

 Breeders of animals use the word "fixity" in this 

 sense. When they have succeeded by repeated judicious 

 " crossing " in obtaining a new character, which they 

 consider valuable, they set about "fixing" it, which 

 process consists in maintaining the original environ- 

 ment as nearly as possible, and permitting no " cross " 

 of fresh blood. When by these means the new char- 

 acter has been transmitted through several generations, 

 the character is said to be " fixed," that is, it has gained 

 a prepotency, has become a prominent character in the 

 animal economy, and is little liable to be lost by re- 

 version. But even when this fixity has been gained, 

 if it is desired to preserve the character, it is necessary 

 that the environment should not be radically changed 

 and that " crossing " should be prevented ; for although 



