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and partly from the similarity, as Kölreuter and others have remarked, between the variability which follows from the crossing of distinct species, and that which may be observed with
plants and animals when reared under new or unnatural conditions. Many facts clearly show how eminently susceptible the reproductive system is to very slight changes in the surrounding conditions. ↑
Nothing is more easy than to tame an animal, and few things more difficult than to get it to breed freely under confinement, even
the
→OMIT
male and female unite. How many animals there are which will not breed, though
→kept in an almost free state
in their native country! This is
→but erroneously, attributed
to vitiated
cultivated plants display the utmost vigour, and yet rarely or never seed! In some few
cases it has been
→discovered that a
very trifling
such as a little more or less water at some particular period of growth, will determine whether or not
plant
I cannot here
→give the
details which I have collected
→and elsewhere published on
this curious subject; but to show how singular the laws are which determine the reproduction of animals under confinement, I may
mention that carnivorous animals, even from the tropics, breed in this country pretty freely under confinement, with the exception of the plantigrades or bear
→which seldom produce young; whereas
carnivorous birds, with the rarest exceptions, hardly ever lay fertile eggs. Many exotic plants have pollen utterly worthless, in the same
condition as in the most sterile hybrids. When, on the one hand, we see domesticated animals and plants, though often weak and sickly,
breeding
freely under confinement; and when, on the other hand, we see individuals, though taken young from a state of
perfectly tamed,
and healthy (of which
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