Chap. XX. SELECTION. 219 



the plum-tree, for instance, some varieties produce plums which 

 are nearly alike, but include stones extremely dissimilar in 

 shape ; whilst conversely other varieties produce dissimilar fruit 

 with barely distinguishable stones ; and generally the stones, 

 though they have never been subjected to selection, differ greatly 

 in the several varieties of the plum. In other cases organs 

 which are not manifestly related, through some unknown bond 

 vary together, and are consequently liable, without any inten- 

 tion on man's part, to be simultaneously acted on by selection. 

 Thus the varieties of the stock (Matthiola) have been selected 

 solely for the beauty of their flowers, but the seeds differ 

 greatly in colour and somewhat in size. Varieties of the 

 lettuce have been selected solely on account of their leaves, 

 yet produce seeds which likewise differ in colour. Generally, 

 through the law of correlation, when a variety differs greatly 

 from its fellow-varieties in any one character, it differs to a 

 certain extent in several other characters. I observed this fact 

 when I cultivated together many varieties of the same species, 

 for I used first to make a list of the varieties which differed 

 most from each other in their foliage and manner of growth, 

 afterwards of those that differed most in their flowers, then in 

 their seed-capsules, and lastly in their mature seed ; and I found 

 that the same names generally occurred in two, three, or four 

 of the successive lists. Nevertheless the greatest amount of 

 difference between the varieties was always exhibited, as far as 

 I could judge, by that part or organ for which the plant was 

 cultivated. 



When we bear in mind that each plant was at first cultivated 

 because useful to man, and that its variation was a subsequent, 

 often a long subsequent, event, we cannot explain the greater 

 amount of diversity in the valuable parts by supposing that 

 species endowed with an especial tendency to vary in any 

 particular manner, were originally chosen. We must attribute 

 the result to the variations in these parts having been succes- 

 sively preserved, and thus continually augmented ; whilst other 

 variations, excepting such as inevitably appeared through corre- 

 lation, were neglected and lost. Hence we may infer that most 

 plants might be made, through long-continued selection, to 

 yield races as different from each other in any character 



