--only we shall ask leave to scrutinise carefully every step of the argument which has such an ending, and demur if at any point of it we are invited to substitute unlimited hypothesis for patient observation, or the spasmodic fluttering flight of fancy for the severe conclusions to which logical accuracy of reasoning has led the way. Now, the main propositions by which Mr. Darwin's conclusion is attained are these:-- 1. That observed and admitted variations spring up in the course of descents from a common progenitor. 2. That many of these variations tend to an improvement upon the parent stock. 3. That, by a continued selection of these improved specimens as the progenitors of future stock, its powers may be unlimitedly increased. 4. And, lastly, that there is in nature a power continually and universally working out this selection, and so fixing and augmenting these improvements. Mr. Darwin's whole theory rests upon the truth of these propositions and crumbles utterly away if only one of them fail him. These, therefore, we must closely scrutinise. We will begin with the last in our series, both because we think it the newest and the most ingenious part of Mr. Darwin's whole argument, and also because, whilst we absolutely deny the mode in which he seeks to apply the existence of the power to help him in his argument, yet we think that he throws great and very interesting light upon the fact that such self-acting power does actively and continuously work in all creation around us. Mr. Darwin finds then the disseminating and improving power, which he needs to account for the development of new forms in nature, in the principle of "Natural Selection," which is evolved in the strife for room to live and flourish which is evermore maintained between themselves by all living things. One of the most interesting parts of Mr. Darwin's volume is that in which he establishes this law of natural selection; we say establishes, because--repeating that we differ from him totally in the limits which he would assign to its action--we have no doubt of the existence or of the importance of the law itself. * * * * *