of viewing them; and thus colour, indicated at first by reference to certain coloured objects, had no fixity. Things which had more definite and purer colours--as certain species of flowers, birds, and insects--were probably too insignificant or too much despised to serve as colour-terms; and even these often vary, either in the same or in allied species, in a manner which would render their use unsuitable. Colour-names, being abstractions, must always have been a late development in language, and their comparative unimportance in an early state of society and of the arts would still further retard their appearance; and this seems quite in accordance with the various facts set forth by Mr. Gladstone and the other writers referred to. The fact that colour-blindness is so prevalent even now, is however an indication that the fully developed colour-sense is not of primary importance to man. If it had been so, natural selection would long ago have eliminated the disease itself, and its tendency to recur would hardly be so strong as it appears to be. _Concluding Remarks on the Colour-sense._--The preceding considerations enable us to comprehend, both why a perception of difference of colour has become developed in the higher animals, and also why colours require to be presented or combined in varying proportions in order to be agreeable to us. But they hardly seem to afford a sufficient explanation, either of the wonderful contrasts and total unlikeness of the sensations produced in us by the chief primary colours, or of the exquisite charm and pleasure we derive from colour itself, as distinguished from variously-coloured objects, in the case of which association of ideas comes into play. It is hardly conceivable that the material _uses_ of colour to animals and to ourselves, required such very distinct and powerfully-contrasted sensations; and it is still less conceivable that a sense of delight in colour _per se_ should have been necessary for our utilization of it. The emotions excited by colour and by music, alike, seem to rise above the level of a world developed on purely utilitarian principles. VII. BY-PATHS IN THE DOMAIN OF BIOLOGY: BEING AN ADDRESS DELIVERED TO THE BIOLOGICAL SECTION OF THE BRITISH ASSOCIATION, (GLASGOW, SEPTEMBER 6TH, 1876,) AS PRESIDENT OF THE SECTION. Introductory Remarks--ON SOME RELATIONS OF LIVING THINGS TO THEIR ENVIRONMENT--The Influence of Locality on Colour in Butterflies and Birds--Sense-perception influenced by Colour of the Integuments--Relations of Insular Plants and Insects--RISE AND PROGRESS OF MODERN VIEWS AS TO THE ANTIQUITY AND ORIGIN OF MAN--Indications of Man’s extreme Antiquity--Antiquity of Intellectual Man--Sculptures on Easter-Island--North American Earthworks--The Great Pyramid--Conclusion.