353
We have now to consider the most important part of
this question,—Are the offspring of hybrids continuously
fertile ?
“‘A hybrid plant,’ says M. Naudin, ‘is an individual in which are
found blended, in an artificial union, two natures which are mutually
opposed, and are continually striving to disengage themselves from
one another.’ ”—(.Aftad P. Flourens. Examen du Livre de M. Darwin.
A 97-)
This assertion is a generalisation, based upon a certain
amount of actual experience. It cannot be reasonably
doubted that, when a hybrid race has been produced,
it has often ceased to exist either through reversion to
one of the parent forms or through inability to continuous
fertility on the part of the race. And there need be no
wonder that it is so! For we know that when members
of the same species are submitted to new conditions, the
effect is very varied on the constitution, especially with
reference to the reproductive organs. Rut the question
which we have now to consider is not whether the off
spring of some hybrids are sometimes infertile or not
continuously fertile, but whether the offspring of some
hybrids are continuously fertile. The following evidence
goes to show that the hybrid offspring of some species
maintain at once their hybridity and their fertility.
“A most attractive group of birds has just been placed by Pro
fessor Flower in the great hall of the Natural History Museum, at
South Kensington. The case is intended to illustrate the hybridisa
tion of species in a state of nature, and the species selected are the
hooded and carrion crows (Corvus cornix and C. corone) and the
European and Asiatic goldfinches {Carduelis elegans and C.orientalis).
The series of these birds has been presented to the Museum by
Mr. Henry Seebohm, who procured the specimens himself during
his travels in Siberia. The case of the crows is one of the few
instances known of actual wild hybridisation, though many more are
suspected, especially among the game birds. It is certain, however,
that wherever the colonies of hooded crows meet the carrion crows
W