mon, and they may arise
either from direct embryonic modifications or apparently from some obscure
change in the parental action. To the former category belong the hosts of
instances of malformation through arrest of development, and perhaps
generally monstrosities of some sort are the result of such affections of
the embryo. To the second category belong all cases of hybridism, of cross
breed, and in all probability the new varieties and forms, such as the
memorable one of the black-shouldered peacock. In all these cases we do not
have abortions or monstrosities, but more or less harmonious forms often of
great functional activity, endowed with marked viability and generative
prepotency, except in the case of hybrids, when we often find even a more
marked generative impotency.

It seems probable therefore that new species may arise from some
constitutional affection of parental forms--an affection mainly, if not
exclusively, of their generative system. Mr. Darwin has carefully
collected[235] numerous instances to show how excessively sensitive to
various influences this system is. He says:[236] "Sterility is independent
of general health, and is often accompanied by excess of size, or {234}
great luxuriance," and, "No one can tell, till he tries; whether any
particular animal will breed under confinement, or any exotic plant seed
freely under culture." Again, "When a new character arises, whatever its
nature may be, it generally tends to be inherited, at least in a temporary
and sometimes in a most persistent manner."[237] Yet the obscure action of
conditions will alter characters long inherited, as the grandchildren of
Aylesbury ducks, removed to a distant part of England, completely lost
their early habit of incubation, and hatched their eggs at the same time
with the common ducks of the same place.[238]

Mr. Darwin quotes Mr. Bartlett as saying: "It is remarkable that lions
breed more freely in travelling collections than in the zoological gardens;
probably the constant excitement and irritation produced by moving from
place to place, or change of air, may have considerable influence in the
matter."[239]

Mr. Darwin also says: "There is reason to believe that insects are affected
by confinement like the higher animals," and he gives examples.[240]

Again, he gives examples of change of plumage in the linnet, bunting,
oriole, and other birds, and of the temporary modification of the horns of
a male deer during