rational and sympathetic training and a social system which gave to all absolute equality of opportunity, might not become useful, contented, and happy members of society, I became much more tolerant. I learnt also to distrust all first impressions; for I repeatedly came to enjoy the society of people whose appearance or manner had at first repelled me, and even in the most apparently trivial-minded was able to find some common ground of interest or occupation. I feel myself that my character has continuously improved, and that this is owing chiefly to the teaching of spiritualism, that we are in every act and thought of our lives here building up a character which will largely determine our happiness or misery hereafter; and also, that we obtain the greatest happiness ourselves by doing all we can to make those around us happy.

As I have referred in various parts of this volume to ideas, or suggestions, or solutions of biological problems, which I have been the first to put forth, it may be convenient if I here give a brief account of the more important of them, some of which have, I think, been almost entirely overlooked.

1. The first and perhaps the most important of these is my independent discovery of the theory of natural selection in 1858, in my paper on "The Tendency of Varieties to depart indefinitely from the Original Type." This is reprinted in my "Natural Selection and Tropical Nature;" and it has been so fully recognized by Darwin himself and by naturalists generally that I need say no more about it here. I have given a rather full account of how it first occurred to me in Chapter XXII. of this work.

2. In 1864 I published an article on "The Development of Human Races under the Law of Natural Selection," the most original and important part of which was that in which I showed that so soon as man's intellect and physical structure led him to use fire, to make tools, to grow food, to domesticate animals, to use clothing, and build houses, the

action of natural selection was diverted from his body to his mind, and thenceforth his physical form remained stable while his mental faculties improved. This paper was greatly admired by Mr. Darwin and several other men of science, who declared it to be entirely new to them; but owing to its having been published in one of my less known works, "Contributions to the Theory of Natural Selection," it seems to be comparatively little known. Consequently, it still continues to be asserted or suggested that because we have been developed physically from some lower form, so in the future we shall be further developed into a being as different from our present form as we are different from the orang or the gorilla. My paper shows why this will not be ; why the form and structure of our body is permanent, and that it is really the highest type now possible on the earth. The fact that we have not improved physically over the ancient Greeks, and that most savage races-even some of the lowest in material civilization-possess the human form in its fullest symmetry and perfection, affords evidence that my theory is the true one.

3. In 1867 I gave a provisional solution of the cause of the gay, and even gaudy colours of many caterpillars, which was asked for by Darwin, and which experiment soon proved to be correct. This is referred to in Chapter XXI. of the present volume, and is fully described in my "Natural Selection and Tropical Nature," pp. 82-86. The principle established in this case has been since found to be widely applicable throughout the animal kingdom.

4. In 1868 I wrote a paper on "A Theory of Birds' Nests," the chief purport of which was to point out and establish a connection between the colours of female birds and the mode of nidification which had not been before noticed. This led to the formulation of the following law, which has been very widely accepted by ornithologists: When both sexes of birds are conspicuously coloured, the nest conceals the sitting bird; but when the male is conspicuously

coloured and the nest is open to view, the female is plainly coloured and inconspicuous. No less than fifteen whole families of birds and a number of the genera of other families belong to the first class, of brightly coloured birds with sexes alike, and they all build in holes or make domed nests. Most of these are tropical, but the woodpeckers and kingfishers are European. In the second class, however brilliant the male may be, if the nest is open to view, the female is always plainly coloured, sometimes so much so as to be hardly recognizable as the same species. This is especially the case in such birds as the brilliant South American chatterers and the Eastern pheasants and paradise birds. This law is of especial value, as showing the exceptional need of protection of female birds as well as butterflies, and the remarkable way in which the colours of both classes of animals have become modified in accordance with this necessity. This paper forms chapter vi. of my "Natural Selection and Tropical Nature."

5. In the great subject of the origin, use, and purport of the colours of animals, there are several branches which, I believe, I was the first to call special attention to. The most important of these was the establishment of the class of what I termed "Recognition colours," which are of importance in affording means for the young to find their parents, the sexes each other, and strayed individuals of returning to the group or flock to which they belong. But perhaps even more important is the use of these special markings or colours during the process of the development of new species adapted to slightly different conditions, by checking intercrossing between them while in process of development. It thus affords an explanation of the almost universal rule, that closely allied species differ in colour or marking even when the external structural differences are exceedingly slight or quite undiscoverable. The same principle also explains the general symmetry in the markings of animals in a state of nature, while under domestication it often disappears: difference of colour or marking on the two sides would render recognition difficult. This principle was first stated in my article on

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"The Colours of Animals and Sexual Selection" (in "Natural Selection and Tropical Nature," 1878) and more fully developed in "Darwinism." I am now inclined to think that it accounts for more of the variety and beauty in the animal world than any other purpose yet discovered.1

I may here add that I believe I was first to give adequate reasons for the rejection of Darwin's theory of brilliant male coloration or marking being due to female choice.

6. The general permanence of oceanic and continental areas was first taught by Professor J. D. Dana, the eminent American geologist, and again by Darwin in his "Origin of Species;" but I am, I believe, the only writer who has brought forward a number of other considerations, geographical and physical, which, with those of previous writers, establish the proposition on almost incontrovertible grounds. My exposition of the subject is given in "Island Life” (chap. vi.), while some additional arguments are given in my "Studies" (vol. i. chap. ii.). The doctrine may be considered as the only solid basis for any general study of the geographical distribution of animals, and it is for this reason that I have made it the subject of my careful consideration.

7. In discussing the causes of glacial epochs I have adopted the general views of Mr. James Croll as to the astronomical causes, but have combined them with geographical changes, and have shown how the latter, even though small in amount, might produce very important results. In particular I have laid stress on the properties of air and water in equalizing temperature over the earth, while snow

1 A correspondent, Mr. G. Norman Douglass, writing from the British Embassy, St. Petersburg, in 1894, sent me the following translation of a passage in Schopenhauer's "Die Welt als Wille und Vorstellung (Zur Teleologie)” which curiously anticipates my views :

"One accounts for the wonderfully varied and vividly glowing coloration of the plumage of tropical birds, although only in a very general way, by the stronger influence of light between the tropics-as its causa efficiens. As its causa finalis, I should say that these brilliant plumages are the full-dress uniforms by means of which the individuals of the numberless species, often belonging to one and the same genus, recognize each other, so that every male finds its female."

and ice, by their immobility, produce cumulative effects; and thus a lowering of temperature of a few degrees may lead to a country being ice-clad which before was ice-free. This is a vital point which is of the very essence of the problem of glaciation; yet it has been altogether neglected in the various mathematical or physical theories which have recently been put forward. My own discussion of the problem in chapter viii. of "Island Life" has never, so far as I know, been controverted, and I still think it constitutes the most complete explanation of the phenomenon yet given.

During a discussion in Nature, so late as 1896, Professor G. H. Darwin and Mr. E. P. Culverwell adduced some new calculations as to the amount of diminished sun-heat due to eccentricity, as invalidating Croll's arguments; whereupon I pointed out that their facts had not the importance they supposed, because they took no account of the cumulative effects of snow and ice above referred to (Nature, vol. liii. p. 220). Sir Robert Ball also, quite independently, made the same objection as myself.

8. In 1880 I published my "Island Life," and the last chapter but one is "On the Arctic Element in South Temperate Floras," in which I gave a solution of the very remarkable phenomena stated by Sir Joseph Hooker in his "Introductory Essay on the Flora of Australia." My explanation is founded on known facts as to the dispersal and distribution of plants, and does not require those enormous changes in the climate of tropical lowlands during the glacial period on which Darwin founded his explanation, and which, I believe, no biologist well acquainted either with the fauna or the flora of the equatorial zone has found it possible to accept. I am informed by my friend Mr. Francis Darwin that this chapter was especially noticed in Germany at the time of its first appearance, but he can hear of no detailed criticism of it, except one by H. von Jhering in Engler's Botan-Fahrbücher (vol. xvii., 1893), of which he has kindly sent me a translation of the more important passages. This is not the place to reply to the criticism, which would require