the summit of this appendage, and in a third species the whole appendage is converted into a horn. In the females of all these species and in the young males the appendage is very minute. The male Chameleon bifurcus has two great solid bony projections, covered with scales, in the upper part of the skull. The male Chameleon Owenii has three great bony horns on his head. These bony horns are covered with a smooth sheath of integument, so that they are strikingly like those of a bull or a goat. In the females and young of both species these appendages are rudimentary.”

BIRDS.-The sexual characteristics of birds are most diversified and conspicuous, and most persons, even those who are not naturalists, know enough of this subject to agree that the males are as a rule much more modified than the females, and it will not be necessary to devote very much space to this group. Darwin has devoted more than two hundred pages to the discussion of the differences between male and female birds, and he has brought together an array of facts all tending to show that male modification is the rule, while female modification is comparatively rare, and although it is true that he gives another explanation of the phenomena, an explanation which will be discussed in the next chapter, yet every reader of his essay must be convinced of the correctness of his conclusion, p. 227, "that weapons for battle, organs for- producing sound, ornaments of many kinds, bright and conspicuous colors, have generally been acquired by the males, the females and the

young being left comparatively but little modified."

This conclusion will be accepted without question by all who are familiar with the subject, and it is hardly necessary to dwell upon it, but the great diversity of the sexual differences in birds demands that in a general

review of the subject they should receive some little notice.

Darwin says: "Male birds sometimes, though rarely, possess special weapons for fighting with each other. They charm the females by vocal and instrumental music of the most various kinds. They are ornamented by all sorts of combs, wattles, protuberances, horns, airdistended sacs, top-knots, naked shafts, plumes and lengthened feathers, gracefully springing from all parts of the body. The beak and naked skin about the head and the feathers are often gorgeously colored. The males sometimes pay their court by dancing, or by fantastic antics, performed either on the ground or in the air. In one instance, at least, the male emits a musky odor, which we may suppose serves to charm or excite the female. The ornaments are wonderfully diversified. The plumes on the front or back of the head consist of variously shaped feathers, sometimes capable of erection or expansion, by which their beautiful colors are fully displayed. Elegant ear-tufts are occasionally present. The head is sometimes covered with velvety down like that of the pheasant, or is naked and vividly colored, or supports fleshy appendages, filaments and solid protuberances. The throat also is sometimes ornamented with a beard, or with wattles or caruncles. Such appendages are generally brightly colored, and no doubt serve as ornaments, though not always ornamental in our eyes: for while the male is in the act of courting the female, they often swell and assume more vivid tints, as in the case of the male turkey. At such times the fleshy appendages about the head of the male Tragopan pheasant swell into a large lappet on the throat and into two horns, one on each side of the splendid top-knot, and these are then colored of the most intense blue which I have ever beheld.

The African hornbill inflates the scarlet bladder-like wattle on its neck, and with its wing drooping and tail expanded makes quite a grand appearance. Even the iris of the eye is sometimes more brightly colored in the male than in the female, and this is frequently the case with the beak, for instance in our common blackbirds. In Buceros corrugatus, the whole beak and immense casque are colored more conspicuously in the male than in the female, and the oblique grooves upon the sides of the lower mandible are peculiar to the male sex. The males are often ornamented with elongated feathers or plumes, springing from almost every part of the body. The feathers on the throat and breast are sometimes developed into beautiful ruffs and collars. The tail feathers are frequently increased in length, as we see in the tail of the Argus pheasant. The body of this latter bird is not larger than that of a fowl, yet the length from the end of the beak to the extremity of the tail is no less than five feet three inches. Nor need much be said. on the wonderful differences of color between the sexes, or on the extreme beauty of the males of many birds. The common peacock offers a striking instance. Female birds of Paradise are obscurely colored and destitute of all ornaments, while the males are probably the most highly decorated of all birds, and in so many ways that they must be seen to be appreciated. The elongated and golden orange plumes which spring from beneath the wings of the Paradisea apoda, when vertically erected and måde to vibrate, are described as forming a sort of halo, in the centre of which the head looks like a little emerald sun, with its rays formed by the two plumes. In another most beautiful species the head is bald and of a rich cobalt blue crossed by several lines of black velvety feathers. Male humming birds almost vie with birds.

of Paradise in their beauty, as every one will admit who has seen Mr. Gould's splendid volumes in his rich collection. It is very remarkable in how many different ways these birds are ornamented. Almost every part of the plumage has been taken advantage of and modified. When the sexes of birds differ in beauty, in the power of singing, or in producing instrumental music, it is almost invariably the male which excels the female."

This extract is enough to show the wonderful diversity of the characteristics of male birds, and the following examples bring out very prominently the fact that male birds of allied species often differ greatly in their sexual characters, while the females are very much alike. In the South American bell-birds the females of the four species resemble each other very closely, and are of a dusky green color, while the male of one species is pure white; in a second species white with the exception of a large space of naked skin on the throat and round the eyes, which during the breeding season is of a fine green color, while in a third species only the head and neck of the male are white and the rest of the body chestnut-brown. In one species the male alone is provided with three filamentous projections half as long as the body, one rising from the base of the beak and the others from the corners of the mouth, while in another species the male has a spiral tube nearly three inches in length which rises from the base of the beak and is jet black dotted over with minute downy feathers. In the Indian chats, honeysuckers, shrikes, kingfishers, Kallij pheasants, and trce partridges, the males of allied species from distinct countries are quite different from each other, while the females and the young of both sexes are indistinguishable.

In the cases where the females of allied species do differ the difference is rarely so great as between the males. Darwin says: "We see this clearly in the whole family of the Gallinacea: the females for instance of the common and Japan pheasant, and especially of the gold and Amherst pheasant, of the silver pheasant and the wild. fowl, resemble each other very closely in color, while the males differ to an extraordinary degree. So it is with the Cotingidae Fringillidae and many other families. There can indeed be no doubt that as a general rule the females have been modified to a less extent than the males." (Variation, Vol. II. p. 184.)

As regards the relation between the young and the adult, the general rule is that when the sexes differ the young of both sexes in their first plumage resemble the adult female as they do in the common fowl or the peacock, or else they resemble her more closely than they do the adult male.

Darwin says that innumerable instances of this law could be given in all orders, but that it will suffice to call to mind the common pheasant, duck, and house sparrow.

There are a few cases in which the young male is like the adult male, and the young female like the adult female, and there are also a few cases where the young of both sexes resemble the adult male, but the difference between the sexes is never, in this case, very great, and in stances are so rare that Darwin, who says that he has recorded all he could find, gives only nine. In his summary he says: "We thus see that the cases in which female birds are more conspicuously colored than the males, with the young in their immature plumage resembling the adult males instead of the adult females, are not numerous, though they are distributed in various orders. The