to inorganic elements."[45] Now, to this elaborate argument in favor of _spontaneous generation,_ or the production of life by natural law, we answer, in the first place, that the mere fact of its being adduced in connection with the Theory of Development affords a conclusive proof that it is indispensable to the maintenance of that theory, that the hypothesis would be incomplete without it, and that no account can be given of creation by the mere doctrine of a _transmutation of species_. It is the more necessary to make this remark, because not a few who embrace the latter doctrine affect to disown the former, and seek to keep it out of view. But the one is as necessary as the other to a complete theory of Natural Development. The author of "The Vestiges" felt this, and virtually acknowledges it when he undertakes the task of vindicating the credibility of spontaneous generation. But we answer, in the second place, that the method in which he performs his self-imposed task is singularly curious, and not a little instructive. He had, it must be owned, a difficult game to play. The general theory of "The Vestiges" is founded on the fact that, in the ordinary course of Nature, the races of plants and animals are perpetuated by propagation, according to established Natural Laws,--a fact which might seem to afford a strong analogical argument in favor of the supposition that the same order of Nature is maintained also in the few apparently exceptional cases in which, from our defective knowledge, we are unable to trace the connection between the parent and the product. And yet the author evinces no little anxiety to make out a case in favor of "a non-generative origin of life even at the present day;" and he appeals to a class of facts, confessedly obscure, which have not been, as he thinks, satisfactorily accounted for by the law which usually regulates the production of organic beings. He refers us to the speculations of Dr. Allen Thomson on the primitive production of Infusoria,[46] to the facts which modern science, aided by the microscope, has discovered respecting the Entozoa, or the creatures which live within the bodies of others, and, above all, to the experiments of Mr. Crosse and Mr. Weekes, which seemed to result in the production of a small species of insect (_Acarus Crossii_) from the action of a voltaic battery on a saturated solution of the silicate of potash, or the nitrate of copper, or the ferrocyanate of potassium. The reason of his anxiety to avail himself of these cases is evident. The exigencies of his theory demanded a method of accounting for the primary origin of life different from any that can be found in the common process of propagation. He saw clearly enough that his main argument, founded, as it was, on the law of hereditary transmission, could not account for the production of the first organism; and that, if he would avoid either the doctrine of _Immediate