VARIATION UNDER DOMESTICATION 31 



CHAPTER I 



VARIATION UNDER DOMESTICATION 



Causes of Variability — Effects of Habit and the use or disuse of Parts — 

 Correlated Variation — Inheritance — Character of Domestic 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 ancienlly fol- 

 lowed, their Effects — Methodical and Unconscious Selection — Un- 

 known Origin of our Domestic Productions — Circumstances favora- 

 ble to Man's power of Selection 



Causes of Variability 



WHEN we compare the individuals of the same 

 variety or sub- variety of our older cultivated 

 plants and animals, one of the first points 

 which strikes us is, that they generally differ more from 

 each other than do the individuals 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 conditions 

 of life not so uniform as, and somewhat different from, 

 those to which the parent species had been exposed 

 under nature. There is, also, some probability in the 

 view propounded by Andrew Knight, that this variability 

 may be partly connected with excess of food. It seems 

 clear that organic beings must be exposed during several 



