688 THE POPULAR SCIENCE MONTHLY. 



preexisting 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 de- 

 grees 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 ele- 

 ment, 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 concep- 

 tions. 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 conject- 

 ures 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 inter- 

 est in science that we have constantly to bear in mind the radical differ- 

 ence obtaining between verified scientific results and analogical scien- 

 tistic 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 reason- 

 ing 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 



