A tendency to sudden reversions to the perfect
character of either parent would, also, be much more likely to occur with
mongrels, which are descended from varieties often suddenly produced and
semi-monstrous in character, than with hybrids, which are descended from
species slowly and naturally produced. On the whole, I entirely agree with
Dr. Prosper Lucas, who, after arranging an enormous body of facts with
respect to animals, comes to the conclusion that the laws of resemblance of
the child to its parents are the same, whether the two parents differ
little or much from each other, namely, in the union of individuals of the
same variety, or of different varieties, or of distinct species.
Independently of the question of fertility and sterility, in all other
respects there seems to be a general and close similarity in the offspring
of crossed species, and of crossed varieties. If we look at species as
having been specially created, and at varieties as having been produced by
secondary laws, this similarity would be an astonishing fact. But it
harmonises perfectly with the view that there is no essential distinction
between species and varieties.
SUMMARY OF CHAPTER.
First crosses between forms, sufficiently distinct to be ranked as species,
and their hybrids, are very generally, but not universally, sterile. The
sterility is of all degrees, and is often so slight that the most careful
experimentalists have arrived at diametrically opposite conclusions in
ranking forms by this test.
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