VARIATION UNDER DOMESTICATION 39 



must have largely favoured the improvement and 

 formation of new breeds. Pigeons, I may add, can be 

 propagated in great numbers and at a very quick rate, 

 and inferior birds may be freely rejected, as when killed 

 they serve for food. On the other hand, cats, from 

 their nocturnal rambling habits, cannot be matched, 

 and, although so much valued by women and children, 

 we hardly ever see a distinct breed kept up ; such 

 breeds as we do sometimes see are almost always im- 

 ported from some other country, often from islands. 

 Although I do not doubt that some domestic animals 

 vary less than others, yet the rarity or absence of 

 distinct breeds of the cat, the donkey, peacock, goose, 

 etc., may be attributed in main part to selection not 

 having been brought into play ; in cats, from the diffi- 

 culty in pairing them ; in donkeys, from only a few 

 being kept by poor people, and little attention paid to 

 their breeding ; in peacocks, from not being very 

 easily reared and a large stock not kept ; in geese, 

 from being valuable only for two purposes, food and 

 feathers, and more especially from no pleasure having 

 been felt in the display of distinct breeds. 



To sum up on the origin of our Domestic Races of 

 animals and plants. I believe that the conditions of 

 life, from their action on the reproductive system, are 

 so far of the highest importance as causing variability. 

 I do not believe that variability is an inherent and 

 necessary contingency, under all circumstances, with 

 all organic beings, as some authors have thought. The 

 effects of variability are modified by various degrees of 

 inheritance and of reversion. Variability is governed 

 by many unknown laws, more especially by that of cor- 

 relation of growth. Something may be attributed to 

 the direct action of the conditions of life. Something 

 must be attributed to use and disuse. The final result 

 is thus rendered infinitely complex. In some cases, I 

 do not doubt that the intercrossing of species, aborigin- 

 ally distinct, has played an important part in the origin 

 of our domestic productions. When in any country 

 several domestic breeds have once been established, 



