intercross

The fully-developed males and females are winged, and individuals from distinct nests can hardly fail often to intercross.

From Effects of Cross and Self Fertilisation in the Vegetable Kingdom by Charles Darwin

There is no doubt that these three pheasants, namely, the common, the true ring-necked, and the Japan, intercross, and are becoming blended together in the woods of several parts of England.

From On the Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life. (2nd edition) by Charles Darwin

Both species are grown in pure form in Korea, and they intercross readily, and we do not regard it as a new species.

From Northern Nut Growers Association Report of the Proceedings at the 44th Annual Meeting Rochester, N.Y. August 31 and September 1, 1953 by Northern Nut Growers Association

But these facts do not make me doubt that it is a general law of nature that the individuals of the same species occasionally intercross, and that some great advantage is derived from this act.

From The Variation of Animals and Plants Under Domestication, Volume II (of 2) by Charles Darwin

Why then do not the varieties occasionally intercross, though this would not often happen, as insects so rarely act in an efficient manner?

From Effects of Cross and Self Fertilisation in the Vegetable Kingdom by Charles Darwin