138 THE THEORIES OF EVOLUTION 



In this sense they are not hypothetical ; they are as real 

 as though they were visible to the eye. Speculation 

 only begins when their shape is to be described. Even 

 then certain affirmations are in order. It can be stated 

 that they are not a miniature likeness of the individual 

 (as the old evolutionist Bonnet imagined them to be) ; 

 nor are they particles of lifeless matter, for unless 

 they were live units, able to assimilate, grow and mul- 

 tiply, they could not endure through all the stages 

 of development or resist certain material changes 

 likely to annihilate them. J 



But how do the determinants impart to cells and 

 tissues the special characters which they represent? 

 Weismann accounts for this by suggesting that the 

 determinants are not the ultimate division of living 

 matter. They themselves are made up of biophors 

 (life-bearers), which are the fundamental units, for 

 they canndt resolve themselves into anything smaller 

 than chemical molecules. These elementary units are 

 endowed with all the attributes of life, nutrition, 

 growth, multiplication and division; in their dimen- 

 sions "they lie far below the limits of visibility"; the 

 smallest protoplasmic granules revealed by the most 

 powerful microscopes contain large numbers of them. 

 They are larger, however, than the chemical molecules 

 of which thev are made up. 



The higher units (ids and determinants), represent 

 respectively the complete individual and its different 



