Chap. L] VARIATION UNDER DOMESTICATION. 



CHAPTEE I. 



VAEIATIOlf TJNDEH DOMESTICATION. 



Causes of Variability — BfEects of Habit and the use or disuse of 

 Parts — Correlated Variation — Inheritance — Character of Do- 

 mestic Varieties — Difficulty of distinguishing between Varieties 

 and Species — Origin of Domestic Varieties from one or more 

 Species — Domestic Pigeons, their Differences and Origin — 

 Principles of Selection, anciently followed, their Effects — 

 Methodical and Unconscious Selection — Unknown Origin of 

 our Domestic Productions — Circumstances favourable to Man's 

 power of Selection. 



Causes of Yariahility. 



When we compare the individuals of the same vari- 

 ety or sub- variety of our older cultivated plants and ani- 

 mals, one of the first points which strikes us is, that they 

 generally differ more from each other than do the in- 

 dividuals of any one species or variety in a state of 

 nature. And if we reflect on the vast diversity of the 

 plants and' animals which have been cultivated, and 

 which have varied during all ages under the most 

 different climates and treatment, we are driven to 

 conclude that this great variability is due to our 

 domestic productions having been raised under condi- 

 tions of life not so uniform as, and somewhat differ- 

 ent from, those to which the parent species had been 

 exposed under nature. There is, also, some probability 

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