of my views of the general theory of protective adaptation. Yet it is undoubtedly the fact that in the best known cases in which the female bird is more conspicuously coloured than the male, it is either positively ascertained that the latter performs the duties of incubation, or there are good reasons for believing such to be the case. The most satisfactory example is that of the Gray Phalarope (Phalaropus fulicarius), the sexes of which are alike in winter, while in summer the female instead of the male takes on a gay and conspicuous nuptial plumage; but the male performs the duties of incubation, sitting upon the eggs, which are laid upon the bare ground. In the dotterell (Eudromias morinellus) the female is larger and more brightly coloured than the male; and here, also, it is almost certain that the latter sits upon the eggs. The turnices of India also have the female larger and often more brightly coloured; and Mr. Jerdon states, in his Birds of India, that the natives report that, during the breeding season, the females desert their eggs and associate in flocks, while the males are employed in hatching the eggs. In the few other cases in which the females are more brightly coloured, the habits are not accurately known. The case of the ostriches and emeus will occur to many as a difficulty, for here the male incubates, but is not less conspicuous than the female; but there are two reasons why the case does not apply the birds are too large to derive any safety from concealment; from enemies which would devour the eggs they can defend themselves by force, while to escape from their personal foes they trust to speed. : We find, therefore, that a very large mass of facts relating to the sexual coloration and the mode of nidification of birds, including some of the most extraordinary anomalies to be found in their natural history, can be shown to have an interdependent relation to each other, on the simple principle of the need of greater protection to that parent which performs the duties of incubation. Considering the very imperfect knowledge we possess of the habits of most extra-European birds, the exceptions to the prevalent rule are few, and generally occur in isolated species or in small groups; while several apparent exceptions can be shown to be really confirmations of the law. Real or apparent Exceptions to the Law stated at page 124 The only marked exceptions I have been able to discover are the following— 1. King crows (Dicrourus). These birds are of a glossy black colour, with long forked tails. The sexes present no difference, and they build open nests. This apparent exception may probably be accounted for by the fact that these birds do not need the protection of a less conspicuous colour. They are very pugnacious, and often attack and drive away crows, hawks, and kites; and as they are semi-gregarious in their habits, the females are not likely to be attacked while incubating. s; 2. Orioles (Oriolidae). The true orioles are very gay birds the sexes are, in many Eastern species, either nearly or quite alike, and the nests are open. This is one of the most serious exceptions, but it is one that to some extent proves the rule; for in this case it has been noticed that the parent birds display excessive care and solicitude in concealing the nest among thick foliage, and in protecting their offspring by incessant and anxious watching. This indicates that the want of protection consequent on the bright colour of the female makes itself felt, and is obviated by an increased development of the mental faculties. 3. Ground thrushes (Pittida). These elegant and brilliantlycoloured birds are generally alike in both sexes, and build an open nest. It is curious, however, that this is only an apparent exception, for almost all the bright colours are on the under surface, the back being usually olive-green or brown, and the head black, with brown or whitish stripes, all which colours would harmonise with the foliage, sticks, and roots which surround the nest, built on or near the ground, and thus serve as a protection to the female bird. 4. Grallina Australis. This Australian bird is of strongly contrasted black and white colours. The sexes are exactly alike, and it builds an open clay nest in an exposed situation on a tree. This appears to be a most striking exception, but I am by no means sure that it is so. We require to know what tree it usually builds on, the colour of the bark or of the lichens that grow upon it, the tints of the ground, or of VI other surrounding objects, before we can say that the bird, when sitting on its nest, is really conspicuous. It has been remarked that small patches of white and black blend at a short distance to form gray, one of the commonest tints of natural objects. 5. Sunbirds (Nectariniida). In these beautiful little birds the males only are adorned with brilliant colours, the females being quite plain, yet they build covered nests in all the cases in which the nidification is known. This is a negative rather than a positive exception to the rule, since there may be other causes besides the need for protection which prevent the female acquiring the gay colours of her mate, and there is one curious circumstance which tends to elucidate it. The male of Leptocoma zeylanica is said to assist in incubation. It is possible, therefore, that the group may originally have used open nests, and some change of conditions, leading the male bird to sit, may have been followed by the adoption of a domed nest. This is, however, the most serious exception I have yet found to the general rule. 6. Superb warblers (Malurida). The males of these little birds are adorned with the most gorgeous colours, while the females are very plain, yet they make domed nests. It is to be observed, however, that the male plumage is nuptial merely, and is retained for a very short time; the rest of the year both sexes are plain alike. It is probable, therefore, that the domed nest is for the protection of these delicate little birds against the rain, and that there is some unknown cause which has led to the development of colour in the males only. There is one other case which at first sight looks like an exception, but which is far from being one in reality, and deserves to be mentioned. In the beautiful waxwing (Bombycilla garrula) the sexes are very nearly alike, and the elegant red wax tips to the wing-feathers are nearly, and sometimes quite, as conspicuous in the female as in the male. Yet it builds an open nest, and a person looking at the bird would say it ought, according to my theory, to cover its nest. But it is, in reality, as completely protected by its coloration as the most plainly coloured bird that flies. It breeds only in very high latitudes, and the nest, placed in fir-trees, is formed chiefly of fir-twigs and lichens. Now the delicate gray and ashy and purplish hues of the head and back, together with the yellow of the wings and tail, are tints that exactly harmonise with the colours of fir leaves, bark, and lichens, while the brilliant red wax tips exactly represent the crimson fructification of the common lichen, Cladonia coccifera. When sitting on its nest, therefore, the female bird will exhibit no colours that are not common to the materials by which it is surrounded; and the several tints are distributed in about the same proportions as they occur in nature. At a short distance the bird would be undistinguishable from the nest it is sitting on, or from a natural clump of lichens, and will thus be completely protected. I think I have now noticed all exceptions of any importance to the law of dependence of sexual colour on nidification. It will be seen that they are very few in number, compared with those which support the generalisation; and in several cases there are circumstances in the habits or structure of the species that sufficiently explain them. It is remarkable also that I have found scarcely any positive exceptions—that is, cases of very brilliant or conspicuous female birds in which the nest was not concealed. Much less can there be shown any group of birds in which the females are all of decidedly conspicuous colours on the upper surface, and yet sit in open nests. The many cases in which birds of dull colours in both sexes make domed or concealed nests do not, of course, affect this theory one way or the other; since its purpose is only to account for the fact that brilliant females of brilliant males are always found to have covered or hidden nests, while obscure females of brilliant males almost always have open and exposed nests. The fact that all classes of nests occur with birds which are dull coloured in both sexes merely shows that these dull colours serve to protect the parents at other times than when sitting on the nest, the structure of which is determined by the requirements of the offspring. If the views here advocated are correct, as to the various influences that have determined the specialities of every bird's nest, and the general coloration of female birds, with their action and reaction on each other, we can hardly expect to find evidence more complete than that here set forth. Nature is such a tangled web of complex relations, that a series of correspondences running through hundreds of species, genera, and families, in every part of the system, can hardly fail to indicate a true casual connection; and when, of the two factors in the problem, one can be shown to be dependent on the most deeply seated and the most stable facts of structure and conditions of life, while the other is a character universally admitted to be superficial and easily modified, there can be little doubt as to which is cause and which effect. Various modes of Protection of Animals But the explanation of the phenomenon here attempted does not rest alone on the facts I have been able now to adduce. In the essay on "Mimicry" it is shown how important a part the necessity for protection has played, in determining the external form and coloration, and sometimes even the internal structure of animals. As illustrating this latter point, I may refer to the remarkable hooked, branched, or star-like spicule in many sponges, which are believed to have the function chiefly of rendering them unpalatable to other creatures. The Holothuridæ or sea-cucumbers possess a similar protection, many of them having anchor-shaped spicules embedded in their skin, as the Synapta; while others (Cuviera squamata) are covered with a hard calcareous pavement. Many of these are of a bright red or purple colour, and are very conspicuous, while the allied Trepang, or Beche-de-mer (Holothuria edulis), which is not armed with any such defensive weapons, is of a dull sand or mud colour, so as hardly to be distinguished from the sea-bed on which it reposes. Many of the smaller marine animals are protected by their almost invisible transparency, while those that are most brightly coloured will be often found to have a special protection, either in stinging tentacles like Physalia, or in a hard calcareous crust, as in the star-fishes. Females of some Groups require and obtain more Protection In the struggle for existence incessantly going on, protection or concealment is one of the most general and most effectual means of maintaining life; and it is by modifications |