importance with reference to detecting the approach of carnivores. But it would also seem to play a part in facilitating mutual recognition between individuals of the same kind. At any rate we often find that social forms are provided, in various parts of the body, with peculiar glands, the secretions of which emit

characteristic odours, often, to us, of disagreeable kind. The Rabbit (Lepus cuniculus) is a case in point, for its "rabbity smell" is due to the products of a pair of glands (perineal glands) in the hinder part of the body. The little Peccaries (Dicotyles) of South America possess a good-sized gland under the skin of the back, the secretion being here a stinking oily fluid, the emanations from which no doubt assist in keeping the members of a troop together.

There is good reason why they should, for, as Beddard says (in The Cambridge Natural History), "they owe, too, their safety from many foes to their sociable habits. Being nocturnal animals they are liable to the attacks of the jaguar, which will speedily overpower and devour a peccary that has strayed from its herd."

toes.

In Deer there is usually a scent-gland (the crumen) opening into a pit below the eye; so also in most Antelopes. The latter may also possess other scent-glands in the groin or between the Bottle-shaped structures of the sort are found between the digits in Sheep (fig. 1107). It is interesting to note that a captive specimen of the Klipspringer Antelope (Oreotragus saltator) has been observed to deliberately deposit upon various objects the secretion that oozes out under its eyes. Such a habit if practised under natural conditions would no doubt help these animals to find one another. But the glands in the feet of Sheep, &c., are of special interest here, for drops of the strong-smelling secretion must constantly be squeezed out on to the ground, leaving a well - marked "trail". Many other examples of scent-glands might easily be given. The exact use no doubt varies in different cases, and may have nothing to do with the social habit proper. For example, an animal may thus be assisted in the search for a mate, and Beddard suggests that some scents are possibly of mimetic nature. The odour of the Musk-Deer is perhaps of this kind, for it may suggest to aggressors the musky smell of the Crocodile, an animal which they would think twice before attacking. Stink-glands as a direct defence have been spoken of elsewhere (see vol. ii, p. 301).

CHAPTER LXIV.

ASSOCIATION OF ORGANISMS-COURTSHIP AND MATING

It is well known that among a number of savage tribes welldeveloped thews and sinews are an invaluable possession to a young man inclined towards matrimony; he has, in short, to fight for a wife. Among civilized human communities good looks play no unimportant part in the matter, though financial considerations are sometimes said to be paramount. We have, in fact, the Law of Battle and the Law of Beauty, both very clearly enunciated by Darwin in the case of animals, and illustrated by a wealth of fact. The former law is admitted by all to have great influence in many cases in deciding which individuals shall mate together, but Wallace, whose opinion in all zoological matters is entitled to the greatest respect, does not think that ornamental males are preferred as partners by those of the opposite sex. The part of his argument, so far as the human species is concerned, is thus expressed (in Darwinism):-"A young man, when courting, brushes or curls his hair, and has his moustache, beard, or whiskers in perfect order, and no doubt his sweetheart admires them; but this does not prove that she marries him on account of these ornaments, still less that hair, beard, whiskers, and moustache were developed by the continued preferences of the female sex. So, a girl likes to see her lover well and fashionably dressed, and he always dresses as well as he can when he visits her; but we cannot conclude from this that the whole series of male costumes, from the brilliantly-coloured, puffed, and slashed doublet and hose. of the Elizabethan period, through the gorgeous coats, long waistcoats, and pigtails of the early Georgian era, down to the funereal dress-suit of the present day, are the direct result of female preference." One is inclined to believe, however, that an average girl does prefer a good-looking young man, and that female preference has had a directive influence on the evolution of male

attire. And there are so many facts supporting the view that the females of many animals are influenced by the ornamental endowments of prospective partners, that the existence of the Law of Beauty will be here taken as provisionally proved. At the same time it must not be applied to explain facts in too sweeping a manner. Every case should be considered on its own merits, and our knowledge of animal habits is so very imperfect that it is easy to fall into error. It is also necessary to carefully avoid the pitfall of unconsciously assuming that the mental endowments of lower animals closely resemble our own. There is no reason to think, for example, that a hen-bird exerts a deliberate choice in the selection of a mate. She may be strongly attracted towards one of several possible partners, and beauty of plumage or voice may have to do with such attraction, but that is not the same thing as "deliberate choice " in the usual sense.

It is only among comparatively specialized animals that the Laws of Battle and Beauty are exemplified, and a few examples will fittingly illustrate the subject.

COURTSHIP AND MATING OF MAMMALS (MAMMALIA)

THE LAW OF BATTLE.-A complete list of species in which the males fight in order to secure mates would be a fairly complete catalogue of Mammals, for in this class the question of Beauty would appear to be subordinate. One would naturally expect combats to be most frequent in cases where the females were comparatively few in number, but as a matter of fact it is better marked among polygamous species, which are necessarily social, though it by no means follows that all gregarious animals are polygamous. Deer and various other Hoofed Mammals afford good illustrations, and as these lead a wandering life it is possible that the practice of polygamy has arisen from the desirability of keeping a herd together, an end to which it is more favourable than monogamy. In nearly all species of Deer the males alone possess antlers, and this is correlated with the fact that they fight furiously together in the struggle to secure mates. In the case of our native Red Deer (Cervus elaphus) the adult stags live by themselves except for about three weeks in the autumn, this being the mating-season. Fierce combats are then frequent, that result in the discomfiture of the weaker males, some of which may be

killed outright. Every victor is able to secure a number of partners, but he has to be continually on the look-out to repel other stags wishing to interfere with his family life, and may have to yield his privileges to an intruder. Might as usual is the only right.

THE LAW OF BEAUTY.-Adult male Mammals are not infrequently distinguished from those of the other sex by the possession

of various ornaments, among which may be mentioned the mane of the Lion and the beard of the Goat. An extreme case is presented by the West African Baboon known as the Mandrill (Papio mormon, fig. 1108), the name of which probably means "man-like baboon". If so, it is rather a libel upon the human species, for the appearance of the adult male is decidedly startling. Either side of the face presents a furrowed blue swelling, the grooves being purple, while between these ornaments is a strip of bright red, passing down to the end of the nose, which is of the same lively hue. A pointed beard of orange yellow completes a scheme of colour that is effective in its way. The large bare

VOL. IV.

104