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colours of plants and animals, or rather their superficial colourations, have always attracted naturalists, generally exciting admiration, and sometimes provoking enquiry. In earlier days problems of this description were disposed of by the invocation of teleology, or the doctrine of design, which afforded no explanation, and simply demonstrated an unknown quantity. The Darwinian epoch introduced what may be called the Utilitarian Theory, by which animal colouration was controlled by "natural selection" for useful purposes in the struggle for existence. In each case design is implied, but in the one it is more or less a theological conception, while in the other it is represented as a natural factor. The result is that teleology has died a natural death, while the Utilitarian Theory has become rampant. The "simple primrose" which was "nothing more" to the amiable teleologist, has developed into the mighty Banian tree by the aid of current theory. We had almost forgotten that colour represented a physical or chemical process, in our estimation of its adaptive and protective nature.

The purpose of Miss Newbigin's book may be said to bring back the subject of colouration in nature to a technical treatment; to remove it from the domain of pure theory; to glance at it throughout the vegetable and animal kingdoms; and to describe its essence without either attempting to explain its purpose, or accepting some other very feasible and popular explanations now current. The differences between pigmental and structural colours are fully explained, and those colours classified. In the first, as is well known, hæmoglobin and chlorophyll play their great parts, while pigments, "which are definitely waste products, or are produced by the modification of waste products," are now Zool. 4th ser. vol. III., January, 1899.