preëxisting substratum—some compound of silicium, for instance. Silicium is evidently a very wonderful substance, strangely like carbon in many respects. It is capable of existing in at least as many similar molecular modifications; and, above all, some of its compounds, though inorganic, occur in the colloid state.
It would not be an extravagant supposition to assume a film of some such colloid compound of silicium floating on the top of the sea, exposed to specific solar influences, imbibing carbonic acid from the air, and being traversed by currents of sea-water, holding carbonate of lime and other salts in solution. Under such favorable circumstances it is not altogether improbable that carbon may have actually by degrees been chemically substituted for silicium, and that thus the first hydrocarbons were allowed slowly to slide into existence.
When we consider what a prominent part silicious and cretaceous organisms play in the history of our globe, it would not be so very astonishing to learn that the inorganic substance has to be looked upon as the original matrix, and not merely as the skeleton of such organisms.
There may have been an age in which silicium was the leading element, followed by an age in which lime ruled organic composition, followed again by an age in which Carbon and Company is the thriving firm, to be supplanted by an age in which nitrogen will be foremost, till this also is forced into the background by phosphorus, etc.
It would not be difficult to fill a volume with plausible reasonings in support of the above nevertheless completely hypothetical conceptions. Side by side with the great and positive truths revealed by the study of incipient motility, truths most scrupulously verified during years of closest application, I would have grudged such fanciful conjectures even the little space here allotted to them, if it had not been my intention to invoke their assistance by way of contrast.
It cannot be too forcibly impressed on all who take an earnest interest in science that we have constantly to bear in mind the radical difference obtaining between verified scientific results and analogical scientistic suggestions. The former represent tasks performed, the latter tasks imposed. The former constitute our accredited store of premises, on the ground of which we may with some safety indulge our reasoning propensities; the latter is the more or less skillful performance under such reasoning license. To reason from premises not verified as forming an integral part in the necessary enchainment of natural events is, however, to move in a world of thought in no way contiguous to the realm of science.
Whoever, therefore, wishes to form an opinion regarding the truths here advanced, whether they be in strict accordance with Nature, or whether they be merely mistaken interpretations, need only to examine monera for himself.
Motility is the key to the understanding of vitality and organization. With little trouble any one can now convince himself that living motion