cases played an important part in giving uniformity of character to all the
members of the same domestic race and of the same natural species, though
largely governed by natural selection and by the direct action of the
surrounding conditions.

ON THE POSSIBILITY OF ALL ORGANIC BEINGS OCCASIONALLY INTERCROSSING.

But it may be asked, can free crossing occur with hermaphrodite animals and
plants? All the higher animals, and the few insects which have been
domesticated, have separate sexes, and must inevitably unite for each birth.
With respect to the crossing of hermaphrodites, the subject is too large for
the present volume, but in the 'Origin of Species' I have given a short
abstract of the reasons which induce me to believe that all organic beings
occasionally cross, though perhaps in some cases only at long intervals of
time. (15/14. With respect to plants, an admirable essay on this subject (Die
Geschlechter-Vertheilung bei den Pflanzen: 1867) has been published by Dr.
Hildebrand who arrives at the same general conclusions as I have done. Various
other treatises have since appeared on the same subject, more especially by
Hermann Muller and Delpino.) I will merely recall the fact that many plants,
though hermaphrodite in structure, are unisexual in function;--such as those
called by C.K. Sprengel DICHOGAMOUS, in which the pollen and stigma of the
same flower are matured at different periods; or those called by me
RECIPROCALLY DIMORPHIC, in which the flower's own pollen is not fitted to
fertilise its own stigma; or again, the many kinds in which curious mechanical
contrivances exist, effectually preventing self-fertilisation. There are,
however, many hermaphrodite plants which are not in any way specially
constructed to favour intercrossing, but which nevertheless commingle almost
as freely as animals with separated sexes. This is the case with cabbages,
radishes, and onions, as I know from having experimented on them: even the
peasants of Liguria say that cabbages must be prevented "from falling in love"