DOGS, RABBITS, PIGS.
MAN, ORIGIN OF HIS ABHORRENCE OF INCESTUOUS MARRIAGES.
FOWLS.
PIGEONS.
HIVE-BEES.
PLANTS, GENERAL CONSIDERATIONS ON THE BENEFITS DERIVED FROM CROSSING.
MELONS, FRUIT-TREES, PEAS, CABBAGES, WHEAT, AND FOREST-TREES.
ON THE INCREASED SIZE OF HYBRID PLANTS, NOT EXCLUSIVELY DUE TO THEIR
STERILITY.
ON CERTAIN PLANTS WHICH EITHER NORMALLY OR ABNORMALLY ARE SELF-IMPOTENT, BUT
ARE FERTILE, BOTH ON THE MALE AND FEMALE SIDE, WHEN CROSSED WITH DISTINCT
INDIVIDUALS EITHER OF THE SAME OR ANOTHER SPECIES.
CONCLUSION.

The gain in constitutional vigour, derived from an occasional cross between
individuals of the same variety, but belonging to distinct families, or
between distinct varieties, has not been so largely or so frequently
discussed, as have the evil effects of too close interbreeding. But the former
point is the more important of the two, inasmuch as the evidence is more
decisive. The evil results from close interbreeding are difficult to detect,
for they accumulate slowly, and differ much in degree with different species;
whilst the good effects which almost invariably follow a cross are from the
first manifest. It should, however, be clearly understood that the advantage
of close interbreeding, as far as the retention of character is concerned, is
indisputable, and often outweighs the evil of a slight loss of constitutional
vigour. In relation to the subject of domestication, the whole question is of
some importance, as too close interbreeding interferes with the improvement of
old races. It is important as indirectly bearing on Hybridism; and possibly on
the extinction of species, when any form has become so rare that only a few
individuals remain within a confined area. It bears in an important manner on