y 



128 THE ORIGIN OF SPECIES 



) » In looking at many small points of difference be- 



tween species, which, as far as our ignorance permits 

 ua to judge, seem quite unimportant, we must not forget 

 that chmate, food, etc., have no doubt produced some 

 direct effect. It is also necessary to bear in mind that, 

 owing to the law of correlation, when one part varies, 

 and the variations are accumulated through natural selec- 

 tion, other modifications, often of the most unexpected 

 nature, will ensue. 



As we see that those variations which, under domesti- 

 cation, appear at aay particular period of life, tend to re- 

 appear 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 their chickens; in the horns of our sheep and 

 cattle when nearly adult; — so in a state of nature natural 

 selection will be enabled to act on and modify organic 

 beings at any age, by the accumulation of variations 

 profitable at that age, and by their inheritance at a corre- 

 sponding age. If it profit a plant to have its seeds more 

 apd more widely disseminated by the wind, I can see no 

 greater difficulty in this being effected through natural 

 selection than in the cotton planter increasing and im- 

 proving by selection the down in the pods on his cotton- 

 trees. Natural selection may modify and adapt the larva 

 of an insect to a score of contingencies, wholly different 

 from those which concern the mature insect; and these 

 modifications may effect, through correlation, the structure 

 of the adult. So, conversely, modifications in the adult 

 may affect the structure of the larva; but in all cases 



