220 THE ORIGIN OF SPECIES 



and have not varied — to natural selection having more 

 or less completely, according to the lapse of time, over- 

 mastered the tendency to reversion and to further vari- 

 ability — to sexual selection being less rigid than ordinary 

 selection — and to variations in the same parts having been 

 accumulated by natural and sexual selection, and having 

 been thus adapted for secondary sexual, and for ordinary 

 purposes. 



Distinct Species present analogous Variations, so that a 

 Variety of one Species often assumes a Character prosper 

 to an allied Species, or reverts to some of the Characters 

 of an early Progenitor 



These propositions will be most readily understood by 

 looking to our domestic races. The most distinct breeds 

 of the pigeon, in countries widely apart, present sub- 

 varieties with reversed feathers on the head, and with 

 feathers on the feet — characters not possessed by the 

 aboriginal rock-pigeon; these then are analogous varia- 

 tions in two or more distinct races. The frequent pres- 

 ence of fourteen or even sixteen tail-feathers in the pouter 

 may be considered as a variation representing the normal 

 structure of another race, the fantail. I presume that no 

 one will doubt that all such analogous variations are due 

 to the several races of the pigeon having inherited from 

 a common parent the same constitution and tendency tc 

 variation, when acted on by similar unknown influences. 

 In the vegetable kingdom we have a case of analogous 

 variation, in the enlarged stems, or as commonly called 

 roots, of the Swedish turnip and Ruta-baga plants which 

 several botanists rank as varieties produced by cultiva- 

 tion from a common parent: if this be not so, the case 



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