No one can tell till he
tries, whether any particular animal will breed under confinement, or any
exotic plant seed freely under culture; nor can he tell till he tries,
whether any two species of a genus will produce more or less sterile
hybrids. Lastly, when organic beings are placed during several generations
under conditions not natural to them, they are extremely liable to vary,
which seems to be partly due to their reproductive systems having been
specially affected, though in a lesser degree than when sterility ensues.
So it is with hybrids, for their offspring in successive generations are
eminently liable to vary, as every experimentalist has observed.
Thus we see that when organic beings are placed under new and unnatural
conditions, and when hybrids are produced by the unnatural crossing of two
species, the reproductive system, independently of the general state of
health, is affected in a very similar manner. In the one case, the
conditions of life have been disturbed, though often in so slight a degree
as to be inappreciable by us; in the other case, or that of hybrids, the
external conditions have remained the same, but the organisation has been
disturbed by two distinct structures and constitutions, including of course
the reproductive systems, having been blended into one. For it is scarcely
possible that two organisations should be compounded into one, without some
disturbance occurring in the development, or periodical action, or mutual
relations of the different parts and organs one to another or to the
conditions of life.
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