And so Lazarus unmoors his fragile boat, and launches it, unmanned and untended, on the bosom of the stream,--to meet its fate. HENRY J. MILLER. THE FORMS AND COLOURS OF LIVING CREATURES. In the Essay on Animals and Plants, which appeared in the September Number of this Review, the names were given of the principal groups in which the prodigious multitude of living creatures (existing or known to have existed) have been classified by naturalists. It was therein also indicated that these various groups, and all the subdivisions of such groups, are distinguished one from another by variations in the forms and structures of the creatures which compose them. This fact alone would prove that very many differences in form must exist; but, indeed, a very slight knowledge and a very cursory examination of animals and plants would suffice to show this even to any one who knew nothing of the scope or nature of biological classification. In truth, to the non-scientific observer who feels an interest in living things, the difficulty may seem to be rather how to find general resemblances than how to detect differences between creatures which seem so totally diverse as do humming birds from whales, bees from buffaloes, or the numerous African herds of antelopes from the grasses on which they feed. Nevertheless it was pointed out in the second Essay of this series[56] that all living creatures do agree to a certain extent in the form and structure of their bodies, inasmuch as their bodies are always bounded by curved lines and surfaces, while, if we divide the body of any animal or plant its structure may always be seen to be heterogeneous--that is to say, composed of different substances, even the simplest showing a variety of minute particles (granules) variously distributed throughout its interior. It has also been pointed out[57] that all living creatures agree in beginning life in the form of a small rounded mass of protoplasm. But all animals and plants further agree in that each kind has its own proper size, shape, structure, and colour, and each (as we shall hereafter see) shows a positive unity in its fundamental constitution, co-existing with the heterogeneity above referred to. But though each kind has its own proper size, shape, structure, and colour, yet these vary more or less in different individuals, and the degrees of variability are different in different kinds both of animals and plants. As to size, although most living creatures have certain limits which they rarely exceed or fall below, yet many organisms vary greatly in this respect. Thus, that familiar weed, the common centaury (_Erythræa centaurium_), may vary in height--according to the soil and other external conditions--from half an inch to five feet.