THE BEGINNINGS OF LIFE. 107 



possible does it seem that this theory can be true. All 

 developmentalists would start in bygone ages with living 

 matter existing in its simplest form or forms ; and this 

 must be supposed to be far more mobile and changeable 

 than crystalline matter. How this latter may vary 

 under the influence of changing conditions we have 

 already shown : we may fairly expect, therefore, that 

 the newly-evolved, primordial, living matter would be 

 even more prone than this has been shown to be, to 

 assume new developmental forms under the influence of 

 changing external conditions. We see our way, there- 

 fore, quite plainly to an advance in the developmental 

 scale, and, owing to the tendency of organisms to re- 

 produce their like (under the influence of Heredity), we 

 may understand how a continual widening of the 

 successive platforms may take place, upon some parts 

 of which further developmental differentiations may be 

 initiated. In their turn, the various diiFerent and often 

 more complex forms thus produced, are multiplied by 

 further reproductive processes, and so on through in- 

 numerable series and ramifications, — organisms being 

 gradually evolved whose complexity makes it more and 

 more diflScult to bring about permanent alterations, 

 even when aided by the powerfully modifying agencies 

 included under the head of ' Natural Selection.^ Longer 

 and longer periods become necessary to induce even 

 slight specific alterations. Change, therefore, is rapid 

 amongst the lower terms of the series, and more and 

 more slow as we ascend in the scale of complexity and 



