54 THE FACTORS OF OEGANIC EVOLUTION. 



the primordial utricle in the one case, and in the other 

 case the layer of active sarcode. In either case the 

 living protoplasm, placed in the position of a lining to the 

 cuticle of the cell, is shielded from the direct action of the 

 medium, and yet is not beyond the reach of its influences. 



Limited, as thus far drawn, to a certain common trait of 

 those minute organisms which are mostly below the reach 

 of unaided vision, the foregoing conclusion appears trivial 

 enough. But it ceases to appear trivial on passing into 

 a wider field, and observing the implications, direct and 

 indirect, as they concern plants and animals of sensible sizes. 



Popular expositions of science have so far familiarized 

 many readers with a certain fundamental trait of living 

 things around, that they have ceased to perceive how 

 marvellous a trait it is, and, until interpreted by the Theory 

 of Evolution, how utterly mysterious. In past times, the 

 conception of an ordinary plant or animal which prevailed, 

 not throughout the world at large only but among the 

 most instructed, was that it is a single continuous entity. 

 One of these livings things was unhesitatingly regarded as 

 being in all respects a unit. Parts it might have, various 

 in their sizes, forms, and compositions ; but these were 

 components of a whole which had been from the beginning 

 in its original nature a whole. Even to naturalists fifty 

 years ago, the assertion that a cabbage or a cow, though 

 in one sense a whole, is in another sense a vast society 

 of minute individuals, severally living in greater or less 

 degrees, and some of them maintaining their independent 

 lives unrestrained, would have seemed an absurdity. But 

 this truth which, like so many of the truths established by 

 science, is contrary to that common sense in which most 

 people have so much confidence, has been gradually 

 growing clear since the days when Leeuwenhoeck and his 

 contemporaries began to examine through lenses the 

 minute structures of common plants and animals. Each 



