12 VARIATION UNDER DOMESTICATION. [Chap. I, 



same plant. These bud variations, as they may be 

 named, can be propagated by grafts, offsets, &c., and 

 sometimes by seed. They occur rarely under nature, 

 but are far from rare under culture. As a single bud 

 out of the many thousands, produced year after year on 

 the same tree under uniform conditions, has been 

 known suddenly to assume a new character; and as 

 buds on distinct trees, growing under different con- 

 ditions, have sometimes yielded nearly the same variety 

 — for instance, buds on peach-trees producing nec- 

 tarines, and buds on common roses producing moss- 

 roses — we clearly see that the nature of the conditions 

 is of subordinate importance in comparison with the 

 nature of the organism in determining each particular 

 form of variationj — perhaps of not more importance 

 than the nature of the spark, by which a mass of com- 

 bustible matter is ignited, has in determining the nature 

 of the flames. 



Effects of Habit and of the Use or Disuse of Parts; 

 Correlated Variation; Inheritance. 



Changed habits produce an inherited effect, as in the 

 period of the flowering of plants when transported from 

 one climate to another. With animals the increased 

 use or disuse of parts has had a more marked influence; 

 thus I find in the domestic duck that the bones of the 

 wing weigh less and the bones of the leg more, in 

 proportion to the whole skeleton, than do the same 

 bones in the wild-duck; and this change may be safely 

 attributed to the domestic duck flying much less, and 

 walking more, than its wild parents. The great and 

 inherited development of the udders in cows and goats 



