420 THE WOELD OP LIFE 



were, a new substance, possessing properties and powers dif- 

 ferent from those of any other substances whatever. These 

 almost infinitely various properties of chemical combinations, 

 together with a host of other problems with which the organic 

 chemist has to deal, have led some of them to almost exactly 

 the same conclusion to which I have been led by a more super- 

 ficial view of the marvels of '' growth " and cell-division in 

 living organisms. In the Address already quoted, Sir H. E. 

 Armstrong says, after referring to some of the complex and 

 extraordinary chemical transformations produced by living 

 plants : 



" The general impression produced by facts such as these is, 

 that directive influences are the paramount influences at work in 

 building up living tissues." 



And again more explicitly : 



" It would seem that control is exercised and stability secured 

 in several ways; not only is the form laid down in advance but 

 certain chosen materials are alone available, and the builders can 

 only unite particular materials in particular ways." 



It is very satisfactory to find that both chemists and 

 physiologists recognise the absolute need of some controlling 

 and directive power in elaborating the special products or 

 building up the complex tissues of plants and animals. 



The Cause and Purpose of this Variety 



The general conclusion to which the whole argument of 

 this volume tends, is, that the infinite variety we see in nature 

 can be traced back step by step to the almost infinite complexity 

 of the cells by means of which they live and gi'ow; of the 

 protoplasm which is the substance of the cells; of the elements 

 of which protoplasm consists ; of the molecules of those 

 elements ; and finally of the atoms whose combination forms 

 the separate and totally distinct elementary molecules. And 

 at each step farther back we are as far ofi^ as ever from com- 



