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Show 276 CONCLUDING REMARKS CHAP. VI. powers. We shall, perhaps, best perceive the complex and extraordinary nature of the marriage arrangements of a trimorphic plant by the following illustration. Let us suppose that the individuals of the same species of ant always lived in triple communities; and that in one of these, a large-sized female (differing also in other characters) lived with six middle-sized and six small-sized males; in ~he second community a middle- , sized female lived with six large- and six small-sized males ; and in the third, a small-sized female lived with six large- and six middle-sized males. Each of these three fe1nales, though enabled to unite with any male, would be nearly sterile with her own two sets of 1nales, and likewise with two other sets of n1ales of the same size with her own which lived in the other two communities ; but she would be fully fertile when paired with a male of her own size. Hence the thirtysix males, distributed by half-dozens in the three communities, would be divided into three sets of a dozen each; and these sets, as well as the three females, would differ from one another in their reproductive powers in exactly the same manner as do the distinct species of the same genus. But it is a still more remarkable fact that young ants raised from any one of the three female ants, illegitimately fertilised by a n1ale of a different size would resemble in a whole series of relations the hybrid offspring from a cross between two distinct species of ants. They would be dwarfed in stature, and more or less, or even utterly _barren. Naturalists are so much accustomed to behold great diversities of structure associated with the two sexes, that they feel no surprise at almost any amount of difference; but differences in sexual nature have been thought to be the very touchstone of specific distinction. We now see that such sexual differences CHAP. VI. ON HETEROSTYLED PLANTS. 277 -t~~ greater or less p~wer of fertilising and being fertilised-may charactense the co-existing individuals of the same species, in the same manner as they characterise and have kept separate those groups of individuals, produced during the lapse of ages, which we rank and denominate as distinct species. |