Origin of Species Variorum

Nevertheless low and simple forms will long endure if well fitted for their simple conditions of life. ↑

Natural selection, on the principle of qualities being inherited at corresponding ages, can modify the egg, seed, or young, as easily as the adult. Amongst many animals, sexual selection will give its aid to ordinary selection, by assuring to the most vigorous and best adapted males the greatest number of offspring. Sexual selection will also give characters useful only to the males, in their struggles with other males; and these characters will be transmitted to one sex or to both sexes, according to the form of inheritance which prevails.

Whether natural selection has really thus acted in ... adapting the various forms of life to their several conditions and stations, must be judged of by the general tenor and balance of the evidence given in the following chapters. But we already see how it entails extinction; and how largely extinction has acted in the worlds history, geology plainly declares. Natural selection, also, leads to divergence of character; for ... the more organic beings diverge in structure, habits, and constitution, by so much can a greater number be supported on the same area,— of which we see proof by looking to the inhabitants of any small spot or to naturalised productions. Therefore, during the modification of the descendants of any one species, and during the incessant struggle of all species to increase in numbers, the more diversified these descendants become, the better will be their chance of succeeding in the battle for life. Thus the small differences distinguishing varieties of the same species, .. steadily tend to increase, till they come to equal the greater differences between species of the same genus, or even of distinct