of their bright plumage; with flowers, bright pods, and shining shells, the bower-birds decorate tents of love for their honeymoon. The mammals woo chiefly by force; the birds are often moved to love by beauty, and mates often live in prolonged partnership with mutual delight and helpfulness. Sixty years before Darwin elaborated his theory of sexual selection, according to which males have grown more attractive because the most captivating suitors were most successful in love, the ornithologist Bechstein noted how the female canary or finch would choose the best singer among a crowd of suitors; and there seems some reason to believe that the female's choice of the most musical or the most handsome has been a factor in progress. Wallace, on the contrary, maintains that the females are plainly dressed because of the fate which has befallen the conspicuous during incubation, and surely they must thus be handicapped. To others it seems more natural to admit that there is truth in both Darwin's and Wallace's conclusions, but to regard the males as stronger, handsomer, or more musical simply because they are males, of more active constitutional habit than their mates. To this view Mr. Wallace himself inclines.

Compared with the lion's thunder, the elephant's trumpeting, or the stag's resonant bass, and the might which lies behind these, or with the warble of the nightingale, the carol of the thrush, the lark's blithe lay, or the mockingbird's nocturne, and the emotional wealth which these express, the challenges and calls of love among other classes of animals are apt to seem lacking in force or beauty. But our human judgment affords no sure criterion. The frogs and newts, which lead on an average a somewhat sluggish life, wake up at pairing time, and croak according to their strength. The males are often furnished with two resonating sacs at the back of the mouth, and how they can croak dwellers by marsh-land know; the North American bullfrog bellows by himself, and the South American tree-frogs hold a concert in the branches.

Of the mating of fishes we know little, but there are some well-known cases alike of display and of tournament. The stickleback fights with his rivals, leads his mate to

the nest by captivating wiles, dances round her in a frenzy,

FIG. 21.-Male and female bird of paradise (Paradisea minor). (From Evolution of Sex; after Catalogue of Dresden Museum.)

and afterwards guards the eggs with jealous care. The

male salmon, with their hooked lower jaws, fight with their rivals, sometimes to the death.

Among insects the love-play is again very lively. Like birds, many of these active animals are very beautiful in colour and form, especially in the male sex, and a display of charms has often been noticed. Like birds, though in a different fashion, some of them are musical, using their hard legs and wing-edges as instruments. The crickets chirp merrily, the cicadas "sing," and the death-watch taps at the door of his mate.

In the summer night, when colours are put out by the darkness, the glow-worm shines brightly on the mossy bank. In the British species (Lampyris noctiluca) the winged male and the wingless female are both luminous; the latter indeed excels in brightness, while her mate has larger eyes. Whatever the phosphorescence may mean to the constitution of the insect, it is certainly a love-signal between the sexes. But we know most about the Italian glow-worm (Luciola italica), of whose behaviour we have a lively picture—thanks to Professor Emery's nocturnal observations in the meadows around Bologna. The females sit among the grass; the males fly about in search of them. When a female catches sight of the flashes of an approaching male, she allows her splendour to shine. He sees the female's signal, and is swiftly beside her, circling round like a dancing elf. But one suitor is not enough. The female attracts a levée. In polite rivalry her devotees form a circle and await the coquette's choice. In the two sexes, Emery says, the colour of the light is identical, and the intensity seems much the same, though the love-light of the female is more restricted. The most noteworthy difference is that the luminous rhythm of the male is more rapid, with briefer flashes; while that of the female is more prolonged, with longer intervals, and more tremulous-illumined symbols of the contrast between the sexes.

While recognising the genuinely beautiful love-making of most birds, we did not ignore that the courtship of most mammals is somewhat rough. So, after admiring the love dances of many butterflies, the merry songs of the grass

hoppers, and the flashing signals of the glow-insects, it is just that we should turn to the strange courtship of spiders, which is less ideal. Of what we may be prepared to find we get a hint from a common experience. Not long ago I found in a gorge some spiders which I had never seen before. Wishing to examine them at leisure, I captured a male and a female, and, having only one box, put them, with misgivings, together. When I came to examine them, however, the male was represented by shreds. Such unnatural conduct, though by no means universal among spiders, is common. The tender mercies of spiders are cruel. We have lately obtained an account of the courtship of spiders from George W. and Elizabeth G. Peckham, from whose careful observations I select the following illustrations:

According to these observers, "there is no evidence that the male spiders possess greater vital activity; on the contrary, it is the female that is the more active and pugnacious of the two. There is no relation in either sex between development of colour and activity. The Lycosida, which are the most active of all spiders, have the least colour-development, while the sedentary orbweavers show the most brilliant hues. In the numerous cases where the male differs from the female by brighter colours and ornamental appendages, these adornments are not only so placed as to be in full view of the female during courtship, but the attitudes and antics of the male spider at that time are actually such as to display them to the fullest extent possible. The fact that in the Attide the males vie with each other in making an elaborate display, not only of their grace and agility, but also of their beauty, before the females, and that the females, after attentively watching the dances and tournaments which have been executed for their gratification, select for their mates the males that they find most pleasing, points strongly to the conclusion that the great differences in colour and in ornament between these spiders are the result of sexual selection."

These conclusions support Darwin's position that the female's choice is a great factor in evolving attractiveness, and are against Wallace's contention that bright colours express greater vitality, and that the females are less brilliant because enemies eliminate the conspicuous. It is quite likely that Darwin's view is true in some cases (e.g. these spiders), and Wallace's conclusion true in others (e.g. birds and butterflies), or that both may be true in