Origin of Species Variorum

to that high degree which is common with so many species, and which is universal with species which have been differentiated to a generic or family rank, will find the subject extraordinarily complex. After mature reflection it seems to me that this could not have been effected through natural selection; for it could not have been of any direct advantage to an individual animal to breed poorly with another individual of a different variety, and thus to leave few offspring; consequently such individuals could not have been preserved or selected. ↑ With sterile neuter insects we have reason to believe that modifications in their structure have been slowly accumulated by natural selection, from an advantage having been thus indirectly given to the community to which they belonged over other communities of the same species; but an individual animal, if rendered slightly sterile when crossed with some other variety, would not thus indirectly give any advantage to its nearest relatives or to any other individuals of the same variety, thus leading to their preservation. From these considerations I infer, as far as animals are concerned, that the various degrees of lessened fertility which occur with species when crossed cannot have been slowly accumulated by means of natural selection. ↑

With plants, it is possible that the case may be different. With very many kinds, insects constantly bring pollen from neighbouring plants of the same or of other varieties to the stigma of each flower; and with some this is effected by the wind. Now, if the pollen of any one variety should become by spontaneous variation in ever so slight a degree prepotent over the pollen of other varieties, so that, when deposited by any means on the stigmas of the flowers of its own variety, it obliterated the effects of previously placed pollen of other varieties, this would certainly be an advantage to the variety; for it would thus escape being bastardised and deteriorated in