dependence, one upon another, and provoke morphological variations which wholly change the aspect of each one of them. "The probosces of bees and of butterflies would be useless to them if there existed no flowers." The teeth of mammals tell what their regimen is. All their structure is likewise derived and by a kind of reaction from it. "The tongue of the ant-bear and its enormous salivary glands can evidently be useful only for the capture of ants, termites, and other insects living in societies. There are insects that never come out of the anthills; some of them are blind, and others can not eat anything but the food with which the ants gorge them." Innumerable parasites have been modified in a similar manner by the animal environment accidentally chosen by them; and all, starting from very different points, have, under the empire of analogous conditions of existence, put on similar characters. It is Darwin's glory to have established that while the physical and organic mediums are incessantly changing and endlessly producing the most varied and most unforeseen conditions, there are none among them to which organisms have not been able to bend themselves with a flexibility almost without limits.
These relations of the being with its medium furnished "the most powerful arguments for the doctrine of final causes. For this doctrine will hereafter be substituted a higher, a broader philosophy, a conception of the living world which will be wonderful only by its majestic simplicity. Every adaptation of a living being to a determined mode of existence has become no longer only a marvel to admire, but is also a problem to be resolved. This study, in fact, is that of the whole of natural history."
At this point is given a brilliant picture, in which, reviewing the great divisions of the animal kingdom, the author designates in each of the dominant forms of living beings the effect of the conditions of their existence. Every type, we may say, is thus formed by these conditions. To them must be attributed not only the variations in detail which only are commonly called adaptations, but the essential traits of the type, "due also to an anterior adaptation, the effects of which have been transmitted from more or less remote ancestors to their posterity." It results from this that the characteristics proceeding from the most ancient adaptations should be and are the most widely spread. And, as it is precisely the degree of generality of a characteristic which gives it its methodical value (the most general have been called dominant by Cuvier), their order of subordination is simply their order of antiquity. "The classifications, of which the dryness was formerly legendary, thus become all-palpitating with historical interest," for they relate to us the series of conditions of which the animal kingdom is the work and the witness.
Must man be excepted from the general operation of these laws? In no way. It is from the natural sciences thus renovated that we must demand, says M. Perrier, "an exact and scientific notion of the