Origin of Species Variorum

Comparison with 1872

the occasional influence of a distinct individual, can be shown to be physically impossible. Cirripedes long appeared to me to present, ... under this point of view, a case of great difficulty; but I have been enabled, by a fortunate chance, .. to prove that two individuals, though both are self-fertilising hermaphrodites, do sometimes cross.

It must have struck most naturalists as a strange anomaly that, both with animals and plants, some species of the same family and even of the same genus, though agreeing closely with each other in .. their whole organisation, .. are ... hermaphrodites, and some .. unisexual. But if, in fact, all hermaphrodites do occasionally intercross, ... the difference between them and unisexual species is, as far as function is concerned, .. very small.

From these several considerations and from the many special facts which I have collected, but which I am unable here .. to give, it appears that with animals and plants an occasional intercross between distinct individuals is a very general, if not universal, law of nature. ↑

Circumstances favourable for the production of new forms through Natural Selection.

This is an extremely intricate subject. A great amount of variability, under which term individual differences are always included, will evidently be favourable. A large number of individuals,

the occasional influence of a distinct individual can be shown to be physically impossible. Cirripedes long appeared to me to present a case of very great difficulty under this point of view; but I have been enabled, by a fortunate chance, elsewhere to prove that two individuals, though both are self-fertilising hermaphrodites, do sometimes cross.

It must have struck most naturalists as a strange anomaly that, in the case of both animals and plants, species of the same family and even of the same genus, though agreeing closely with each other in almost their whole organisation, yet are not rarely, some of them hermaphrodites, and some of them unisexual. But if, in fact, all hermaphrodites do occasionally intercross with other individuals, the difference between hermaphrodites and unisexual species, as far as function is concerned, becomes very small.

From these several considerations and from the many special facts which I have collected, but which I am not here able to give, I am strongly inclined to suspect, that, both in the vegetable and animal kingdoms, an occasional intercross with a distinct individual is a law of nature. I am well aware that there are, on this view, many cases of difficulty, some of which I am trying to investigate. Finally then, we may conclude that in many organic beings, a cross between two individuals is an obvious necessity for each birth; in many others it occurs perhaps only at long intervals; but in none, as I suspect, can self-fertilisation go on for perpetuity.

Circumstances favourable to Natural Selection.

This is an extremely intricate subject. A large amount of variability will evidently be favourable for the work of natural selection, but mere individual differences probably suffice. A large number of individuals,