lung, it has yet so many parts of its anatomy that are piscine as to lead Professor Huxley still to place it as a solitary representative of the highest order of Pisces.

The class Amphibia is itself a confirmation of the general truth, for its members, such as the frogs, are in their early condition fish, and in their adult state reptiles. Pterodactyl of the Jurassic strata is the winged lizard. Its name tells us that we have a form intermediate between the classes Reptilia and Aves. The duck-billed Platypus, or Ornithorhyncus, of Australia, is a furred mammal that suckles its young, and yet has a bird's bill, a bird's feet, a bird's wishing-bone, a bird's heart, a bird's alimentary canal. If we turn to the individual classes, the same thing obtains. To take but the the highest class, the Prosimiae, or half-apes, among the Mammalia are an order, that stands centrally to the Insectivora, Eodentia, Cheiroptera, and Primates. There is no gap between man and the rest of the Primates. Not a single mark of anatomy, of physiology, or of psychology, clearly distinguishes man from the highest apes.

If we study the individual animal, the same fact of the unity of phenomena is again borne in upon us. The bodily functions are by no means so distinct in their nature as we were wont to think. To take but an illustration.

The sense-organs of man are all found to be only so many modifications of the integument.

The skin or tactile organ is the integument. The tongue or taste organ is but the integument folded inwards and a little modified. The nasal cavities are also lined with a modification of the same tissue, and even the most complex sense organs that are at the same time the most important—that is the eye and the ear—are, as the study of development or embryology shows us, only the result of a series of remarkable changes affecting certain parts of the epidermis of the animal.

Those physiological functions of the human body that appear to be clearly marked off are really not completely demarcated. Take as example the excretory action of the skin, lungs, and the renal organs. The lungs get rid especially of carbon dioxide; the skin of water; the renal organs of the products of nitrogenous decay. But each of these organs also eliminates those products which are eliminated by the other two. Thus the lungs, whilst they get rid principally of carbon dioxide, also get rid of water in the form of steam and of nitrogenous matter. The skin gives off a certain quantity of carbon dioxide and nitrogen excreta. And the renal organs also eliminate all three of the chief forms of excretory matter. When any one of these three organs is not functioning at its best, extra work is thrown upon the others, and in some extreme cases this metastasis, or transference of function, is very remarkable. Thus an ulcer in the human body has been known to secrete milk.

Try to realise at least something of what all this means. It is no longer possible to mark off clearly the various domains of science. Science is one, for it is the study of nature, and nature is one. In every branch of our knowledge that daily grows more unified, the transitions are found to be innumerable and the gradations infinitesimal. Our chemical groups, our geological rocks and strata, our inorganic and organic kingdoms, our plants and animals, our classes, orders, genera, species, all are seen to be artificial.

Here is then the new message that science is uttering to man. It is in truth good news. There is no break anywhere. The universe is one vast whole. It is true that at first there seems to be a loss because of the indistinctness that now veils the old lines of demarcation. At first some taring of a shock is felt when we realise that the old definitions and classifications are only matters of convenience, and really represent nothing in nature. But our view of the whole gains incomparably. We are led to take a larger and more true conception of the universe. If the subdivisions disappear the unity of the whole comes out with