What makes this argument irresistible is the additional fact, first pointed out by Darwin, that plants which are not visited by insects, but are fertilised by the agency of the wind, are neither adorned with beautifully-coloured flowers, nor provided with honey or fragrance. And another most important fact: Darwin found that flowers which depend on the wind for their fertilisation follow the natural tendency of objects to a symmetrical form; whereas the irregular flowers are always those fertilised by insects or birds. This points to the conclusion that insects and birds are responsible not only for the colours and fragrance of flowers, but also for the shape of those that are most unique and fantastic. And this _a priori_ inference is borne out by thousands of curious and most fascinating observations described in the works of Darwin, Lubbock, Müller, and many others. The briefest and clearest presentation of the subject is in Lubbock’s _Flowers, Fruits, and Leaves_, which no one interested in natural æsthetics should fail to read. There is indeed no more interesting study in biology than the mutual adaptation of flowers, bees, butterflies, humming-birds, etc.; for just as these animals have modified the forms of flowers, so the flowers have altered the shape of these animals. Many of the changes in the shapes of flowers are made not only with a view to facilitate the visits of winged insects, but also for keeping out creeping intruders, such as ants, which are very fond of honey, but which, as they do not fly, would not aid the cause of cross-fertilisation. Of these contrivances, “the most frequent are the interposition of _chevaux de frise_, which ants cannot penetrate, glutinous surfaces which they cannot traverse, slippery slopes which they cannot climb, or barriers which close the way.” How obtuse are those who, with Ruskin and Emerson, accuse science of destroying the poetry of nature! What poetry is there in the thought that flowers were made for unæsthetic man, when not one man in a thousand ever takes the trouble to examine one, while for every single flower on which a human eye ever rests, a million are born to blush unseen? But if we abandon the narrow anthropocentric point of view, and admit that insects too have a right to live, how the scope of Nature’s poetry widens! How easy it then becomes to share not only Wordsworth’s belief that “every flower enjoys the air it breathes,” but to endow it with a thousand thoughts and emotions like our own—delight in a gaily-coloured floral envelope; hope that yonder gaudy butterfly will be attracted by it; anxiety lest that “horrid” ant may steal some of its honey; determination to breathe the sweetest perfume on this darling honey bee, so as to induce it to speedily call again.