But there is one point to which we wish to call attention as regards the different method in which the changes of species are treated by Mr. Spencer and Mr. Darwin. The former regards all changes as necessitated by the laws of the moving equilibrium, so that a change of climate of such a nature as to deprive an organism of the requisite moisture for continued existence through a long period of time, would absolutely necessitate some device on its part to counterbalance the external force of drought. It would be a consequent in the very nature of things that the plant should become thick and succulent like the cactus, or that the animal should form for itself a reservoir for the storage of water. Mr. Darwin's theory is very different. He advances the fact that organisms, and more particularly those of the lower and simpler forms constantly produce "sports." These are not chance accidents in the false metaphysical sense of being uncaused, but are termed accidents as being produced by some external or internal incident in the growth of the embryo, which causes it to deviate in some point from the structure of the parent. This "sport" may be to the advantage or to the detriment of the new organism. If it should be the latter, it soon perishes: but if it should assist the organism to a fuller life, then it will live longer and better, and its progeny will in like manner survive to the detriment of its fellows of the unimproved type. The accretion of changes produced in this way, now in one direction, and now in another, together with the influences elsewhere indicated, might do and no doubt has done much in the development of species.