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Show 314 f:iF.XUAJ, f:iELECTION: lUAMl\fALS. PAltT TI. without tho aiel of solectjon. But when tho colours <tl'<' diversified and strongly pronounced, when they arc not developed until ncar maturity, and when they arc lost after emasculation, we can hardly avoid the conclusion that they have been acquired through sexual selection fo1· the sake of ornament, and have been transmitted exclusively, or almost cxclnsivcly, to tho same srx. vVhon both sexes arc coloured in the same manner, and tho colours are conspicuous or curiously arranged, without being of the lea. t apparent use as a protection, and especially when they arc associated with variom; other ornamental appendages, we are led by analogy to the same conclusion, namely, that they have been acquired through sexual selection, although transmitted to both sexes. ~rhat conspicuous aml diversified colours, whether confined to the males or common to both sexes, arc as a general rule associated in tho same groups and subgroups with other econdary sexual characters, serving for war or for ornament, will be found to hold good if we look back to the various cases given in this and the last chapter. The law of tho equal transmission of characters to both sexes, as far as colour and other ornaments arc concerned, bas prevailed far more extensively with mammals than with birds; but in regard to weapous, ,'nch as horns and tusks, these have often been transmitted either exclusively, or in a much higher degree to the males than to the females. This is a surprising circumstance, for as the males generally use their ·weapons as a defence against enemies of all kinds, these weapons would have been of service to the female. Their absence in this sex can be accounted for, as far as we can see, only by the form of inheritance which has prevailed. :Finally with quadrupeds the CnAP. XVIII. SUMMARY. 315 contest between tho individuals of the same sox, whether pcnceful or bloody, has with the rarest exceptions been confined to the males; so that these have been modified through sexual selection, either for fighting with each other or for alluring the opposite sex, far more commonly than the females. |