Of aquatic animals, there are many self-fertilising hermaphrodites; but here the currents of water offer an obvious means for an occasional cross. 查尔斯·达尔文.物种起源.
Turning for a brief space to animals: various terrestrial species are hermaphrodites, such as the land-mollusca and earth-worms; but these all pair. 查尔斯·达尔文.物种起源.
But still there are many hermaphrodite animals which certainly do not habitually pair, and a vast majority of plants are hermaphrodites. 查尔斯·达尔文.物种起源.