128 Darwin, and after Darwin. 



If the advantage of freedom from competition in any given 

 variation depends on the possession, in some degree, of new 

 adaptations to unappropriated resources, there must be some 

 cause that favours the breeding together of those thus specially 

 endowed, and interferes in some degree with their crossing 

 with other variations, or, failing this, the special advantage will 

 in succeeding generations be lost. As some degree of Inde- 

 pendent Generation is necessary for the continuance of the 

 advantage, it is evident that the same condition is necessary 

 for the accumulation through Natural Selection of the powers 

 on which the advantage depends. The advantage of divergence 

 of character cannot be retained by those that fail to retain the 

 divergent character; and divergent character cannot be retained 

 by those that are constantly crossing with other kinds ; and the 

 prevention of free crossing between those that are equally 

 successful is in no way secured by Natura Selection. 



So much, then, as expressive of Mr. Gulick's 

 opinion upon this subject. To exactly the same 

 effect Professor Lloyd Morgan has recently published 

 his judgement upon it thus : — 



That perfectly free intercrossing, between any or all of the 

 individuals of a given group of animals, is, so long as the 

 characters of the parents are blended in the offspring, fatal to 

 divergence of character, is undeniable. Through the elimination 

 of less favoiu-able variations, the swiftness, strength, and 

 cunning of a race may be gradually improved. But no form of 

 elimination can possibly differentiate the group into swift, 

 strong, and cunning varieties, distinct from each other, so long 

 as all three varieties freely interbreed, and the characters of 

 the parents blend in the offspring. Elimination may and does 

 give rise to progress in any given group, as a group ; it does 

 not and cannot give rise to differentiation and divergence, so 

 long as interbreeding with consequent interblending of characters 

 be freely permitted. Whence it inevitably follows, as a matter 

 of simple logic, that where divergence has occurred, inter- 

 crossing and interbreeding must in some way have been 

 lessened or prevented. Thus a new factor is introduced, that 



