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stock of Mr Bakewell for upwards of fifty years. There is not a suspicion existing in the mind of any one at all acquainted with the subject, that the owner of either of them has deviated in any one instance from the pure blood of Mr Bakewell's flock, and yet the difference between the sheep possessed by these two gentlemen is so great that they have the appearance of being quite different varieties.
The Accumulation of Variations by Sexual Selection. -In many species of animals where the sexes are conspicuously different, the males appear to have the advantage: among cattle they have the stronger horns, among birds the brighter plumage and finer power of song; with certain species of beetle, again, they have the more powerful weapon, and with butterflies the gaudier wings. Many of these differences can be accounted for by the continuous operation of two processes, which may be called (1) the Choice of Mates; and (2) the Law of Battle, of which the first bears some analogy to methodical selection in man, and the second to man's unconscious selection: or perhaps it would be truer to say that both correspond to man's unintentional selection.1
(1.) The Choice of Mates, or Contest of Beauty-Many of the lower creatures possess sufficient intelligence to show their preference for one mate rather than another at the breeding season. This is particularly the case with birds, and some instances from that class may suffice for our present purpose. As already intimated, when the sexes differ in beauty, or in the power of sing
1 More strictly, both correspond to sexual selection in man. But sexual selection in man is partly methodical and partly un
CONTEST OF BEAUTY.
ing, it is almost invariably the male which excels the female; and apparently he is thus endowed for the purpose of charming or exciting the female. At the breeding season he elaborately displays his varied attractions, and often performs strange antics on the ground, or in the air, in her presence. It is stated on the authority of the Rev. Darwin Fox, that the common magpie used to assemble from all parts of Delamere Forest, in order to celebrate the "great magpie marriage," the ceremonies consisting in chattering, bustling, and flying about the trees, and sometimes in fighting. The whole affair was evidently considered by the birds as being of the highest importance; and shortly after the meeting they all separated, and were observed to be paired for the season. With Birds of Paradise a dozen or more full-plumaged males congregate in a tree to hold a dancing-party, as the natives call it. They raise their wings, stretch out their necks, elevate their exquisite plumes, and between whiles they fly across from branch to branch in great excitement, so that the whole tree is filled with waving plumes, in every variety of attitude and motion. These birds, when kept in confinement in the Malay Archipelago, are said to take much care in keeping their feathers clean; often spreading them out, examining them, and removing every speck of dirt. One observer, who kept several pairs alive, did not doubt that the display of the male was intended to please the female. The gold pheasant during his courtship not only expands and raises his splendid frill, but turns it obliquely towards the female, on whichever side she may be standing, obviously in order that a large surface may be displayed before her. The male Argus pheasant displays his elegant primary wing-feathers, and
erects his ocellated plumes in the right position for their full effect. The peacock displays his gorgeous train, and struts about in all the pomp of pride, before the female. The goldfinch exhibits alternately his gold-bespangled wings; the common pigeon inflates his breast to show off his iridescent feathers to the best advantage.
As male birds display with so much care their fine plumage and other ornaments in the presence of the females, it is obviously probable that these appreciate the beauty of their suitors. Mr Hussey has described a tame partridge which seemed fond of gay colours, and states that no new gown or cap could be put on without catching its attention. In a state of nature, the female bird is pursued by many males, and so has the opportunity of exerting a choice. Audubon, who spent a long life in observing the habits of birds in the forests of the United States, speaking of a woodpecker, says that the hen is followed by half-a-dozen gay suitors, who continue performing strange antics, until a marked preference is shown for one. The same naturalist carefully observed the wild flocks of Canada geese, and gives a graphic description of their love-antics: he says that the birds which had been previously mated renewed their courtship as early as the month of January, while the others would be contending or coquetting for hours every day, until all seemed satisfied with the choice they had made; after which, although they remained together, any person could easily perceive that they were careful to keep in pairs. Many similar statements could be cited from the most eminent naturalists; and they seem sufficient to prove that the female bird exerts a choice, and receives the addresses of the male who pleases her most. It is not necessary to suppose that she consciously deliberates,
that she studies each spot and stripe of colour, and appreciates fine shading and exquisite patterns; she is probably struck only by the general effect, and is excited and attracted by the most beautiful, melodious, and gallant of her suitors.
It will probably be admitted that the choice of mates -a form of sexual selection which is always at work— must result after sufficient lapse of time in modifications of plumage corresponding to those which man produces methodically, and still more perhaps to those which he produces unintentionally. It is considered that the enormous differences between the sexes in regard to plumage and song,-as, for instance, the superiority of the peacock to the peahen, and of the male canary to the female, are the result of sexual selection, acting on the small differences constantly supplied by nature, the distinguishing marks being inherited by the male sex only; or, if tending to be inherited by the female also, being prevented by other causes from developing.
(2.) The Struggle for Mates, or Law of Battle: It was mentioned just now that magpies sometimes fight as well as chatter at the pairing season. Almost all male birds are extremely pugnacious, using their beaks, wings, and legs for fighting together, and this disposition shows itself most strongly at the breeding season. The males of the common water-hen, when pairing, struggle violently for the females, standing nearly upright in the water, and fighting with their feet. Two were seen to be thus engaged for half an hour, until one got hold of the head of the other, which would have been killed had not the observer interfered-the female all the time looking on as a quiet spectator. The males of many gallinaceous birds, especially of the polygamous
kinds, are furnished with special weapons for fighting with their rivals, namely, spurs, which can be used with fearful effect. It has been recorded by Mr Hewitt that, in Derbyshire, a kite struck at a game-hen accompanied by her chickens, when the cock rushed to the rescue, and drove his spur right through the eye and skull of the aggressor. The males of some birds, as already mentioned, are ready to fight whenever they meet; but generally the season of love is that of battle, the suitors trying to drive away or kill their rivals before they pair. Of course in such struggles the larger and stronger bird, and the best furnished with weapons, has the advantage, secures the female, and leaves offspring which tend to inherit the same characters.
With mammals, the male appears to win the female much more through the law of battle than through the display of his charms. All male animals which are furnished with special weapons for fighting are well known to engage in fierce contests; and the most timid animals, not provided with special weapons, engage in desperate conflicts during the season of love. Two male hares have been seen to fight together until one was killed; male moles often fight, and sometimes with fatal results; male squirrels engage in frequent contests, and often wound each other severely; and male beavers struggle till hardly a skin is without scars. The courage and the desperate conflicts of stags have often been described their skeletons have been found in various parts of the world with the horns inextricably locked together, showing how miserably the victor and the vanquished had perished. The law of battle prevails with aquatic as well as with terrestrial mammals. It is notorious how desperately male seals fight during the