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Show 258 THE PRINCIPLES OF PART II. possessed by the males for fighting with an:l drivin? away their rivals-their courage and pugnae1ty-t~e1r ornaments of many kinds-their organs for producmg vocal or instrumental music -and their glands for emitting odours · most of these latter structures serving only to all~re or excite the female. That ~hese characters are the result of sexual and not of ordmary selection is clear, as unarmed, unornamented, ~r unattractive males would succeed equally well m th~ battle for life and in leaving a numerous progen.y, 1f better endowed males were not present. We may mfer that this would be the case, for the females, which are unarmed and unornamented, are able to survive and procreate their kind. Secondary sexual. charact.ers of the kind just referred to, will be fully discussed m t~e following chapters, as they are in many respects mteresting, but more especially as they depend on the will choice and rivalry of the individuals of either sex. Wh~n we behold two males fighting for the possession of the female, or several male birds displaying their gorgeous plumage, and performing the strangest antics before an assembled body of females, we cannot doubt that, though led by instinct, they know what they ~re about, and consciously exert their mental and bodily powers. In the same manner as man can improve the breed of his game-cocks by the selection of those birds which are victorious in the cockpit, so it appears that the strongest and most vigorous males, or those provided with the best weapons, have prevailed under nature, and have led to the improvement of the natural breed or species. Through repeated deadly contests, a slight degree of variability, if it led to some advantage, however slight, would suffice for the work of sexual selection ; and it is certain that secondary sexual characters ·CnAP. VIII. SEXUAL SELECTION. 259 are eminently variable. In the same manner as man can give beauty, according to his standard oftaste, to his male poultry-can give to the Sebright bante.m a new an~ elegant pluma?'e, an erect and peculiar carriage ·so 1~ appears that m a state of nature female birds, by havmg long selected the more attractive males have adde_d t~ t~eil·. beauty. No doubt this implies ~owers of d1scr1mmatwn and taste on the part of the female which will at first appear extremely improbable; but I hope hereafter to shew that this is not the case. From our ignorance on several points, the precise manner in which sexual selection acts is to a certain extent uncertain. Nevertheless if those naturalists who already believe in the mutability of species, will read the following chapters, they will, I think, agree with ~e that .sexual selection has played an important part m the history of the organic world. It is certain that with almost all animals there is a struggle between the males for the possession of the female. This fact is so notorious that it would be superfluous to give instances. Hence the females, supposing that their mental capacity sufficed for the exertion of a choice, could select one out ?f .several males. But in numerous cases it appears as If It had been specially arranged that there should be a. struggle between many males. Thus with migratory bn·ds, the males generally arrive before the females at their place of breeding, so that many males are ready to contend for each female. The bird-catchers assert that this is invariably ~he case with the nightingale and blackcap, as I am mformed by Mr. Jenner Weir, who. confirms the statement with respect to the latter species. Mr. Swaysland of Brighton, who has been in the habit d~ring the last forty years, of catching our migrator; birds on their first arrival, writes to me that he has s 2 |