CiiM-. IV. NATURAL SELECTION. 89 



stant. Nor ougbt we to think that the occasional destruction 

 of an animal of any particular color would produce little effect : 

 we should remember how essential it is in a flock of white 

 slicep to destroy every lamb with the faintest trace of black. 

 A\'e have seen how the color of the ho<^s, when fcedino: on the 

 " paint-root " in Florida, determines whether they shall live or 

 die. In plants the down on the fruit and the color of the flesh 

 are considered by botanists as characters of the most trifling 

 importance : yet we hear from an excellent horticulturist, Down- 

 ing, that in the United States smooth-skinned fruits sullcr far 

 more from a beetle, a curculio, than those Avith down ; that pur- 

 ple plums suffer far more from a certain disease than 3X'llow 

 plums ; whereas another disease attacks yellow-fleshed peaches 

 far more than those with other colored flesh. If, with all the 

 aids of art, these slight differences make a great difl'crence in 

 cultivating the several varieties, assuredly, in a state of nature, 

 where the trees would have to struggle with other trees and 

 with a host of enemies, such differences would effectually settle 

 whicli variety, whether a smooth or downy, a yellow or purple 

 fleshed fruit, should succeed. 



In looking at many small points of difference between spe- 

 cies, which, as far as our ignorance permits us to judge, seem 

 quite unimportant, we must not forget that climate, food, etc., 

 may have produced some direct eflect. It is also necessary to 

 bear in mind that, owing to the law of correlation, Avhen one 

 part varies, and the A\ariations are accumulated through natural 

 selection, other modifications, often of the most unexpected 

 nature, avUI ensue. 



As we see that those variations Avhicli under domestication 

 appear at any particular })eriod of life, tend to rcapjwar in the 

 offspring at the same period — for instance, in the shape, size, 

 and flavor of the seeds of the many varieties of our culinary 

 and agricultural plants ; in the caterpillar and cocoon stages 

 of the varieties of the silk-worm ; in the eggs of poultry, and in 

 the color of the down of tlieir chickens; in the horns of our 

 sheep and cattle when nearly adult — so, in a state of nature, 

 natural selection Avill be enabled to act on and modify organic 

 beings at any age, by the accumulation of variations profitable 

 j-t that age, and by their inheritance at a corresponding age. 

 If it profit a plant to have its seeds more and more Avidely dis- 

 seminated by the wind, I can sec no greater difliculty in this 

 being effected tlirough natural selection than in the cotton- 

 planter increasing and improving by selection the down in the 



