OF NA TUBAL SELECTION. 2 7 1 



moditications of structure or instinct to its progeny. It 

 may well be asked how it is possible to reconcile this case 

 with the theory of natural selection? 



First, let it be remembered that we have innumerable in- 

 stances, both in our domestic productions and in those in 

 a state of nature, of all sorts of diiferences of inherited 

 structure which are correlated with certain ages and with 

 either sex. We have differences correlated not only with 

 one sex, but Avith that short period when the reproductive 

 system is active, as in the nuptial plumage of many birds, 

 and in the hooked jaws of the male salmon. AVe have even 

 slight differences in the horns of different breeds of cattle 

 in relation to an artificially imperfect state of the male 

 sex, for oxen of certain breeds have longer horns than the 

 oxen of other breeds, relatively to the length of the horns 

 in both the bulls and cows of these same breeds. Hence, 

 I can see no great difficulty in any character becoming cor- 

 related with the sterile condition of certain members of 

 insect communities; the difficulty lies in understanding 

 how such correlated modifications of structure could have 

 been slowly accumulated by natural selection. 



This difficulty, though appearing insuperable, is 

 lessened, or, as I believe, disappears, when it is remem- 

 bered that selection may be applied to the family, as well 

 as to the individual, and may thus gain the desired end. 

 Breeders of cattle wish the flesh and fat to be well marbled 

 together. An animal thus characterized has been slaugh- 

 tered, but the breeder has gone with confidence to the 

 same stock and has succeeded. Such faith may be placed in 

 the power of selection that a breed of cattle, always yield- 

 ing oxen with extraordinarily long horns, could, it is prob- 

 able, be formed by carefully watching which individual 

 bulls and cows, when matched, produced oxen with the 

 longest horns; and yet no one ox would ever have propa- 

 gated its kind. Here is a better and real illustration: 

 According to M. Verlot, some varieties of the double 

 annual stock, from having been long and cai'efully selected 

 to the right degree, always produce a large proportion of 

 seedlings bearing double and quite sterile flowers, but they 

 likewise yield some single and fertile plants. Tliese latter, 

 by which alone the variety can be propagated, may be 

 compared with the fertile male and female ants, and the 



