118 THE THEORIES OF EVOLUTION 



tion), characteristic of a certain organism and, there- 

 fore, can only produce a similar organism. Between 

 the whole and its parts there is not only a bond but 

 a deep identity; differences are only quantitative. 



However interesting these theories may be in their 

 bearing upon the constitution of the protoplasm and 

 the nature of vital phenomena, they account but 

 vaguely for the transmission of characters. 



For more definite explanations we must turn to the- 

 ories according to which the hypothetical particles are 

 not only endowed with mere molecular energy or with 

 general properties, but are supposed to represent dis- 

 tinct parts or distinct properties of the organism. 

 In such theories we will find the most inclusive, accu- 

 rate and fruitful ideas about heredity. Foremost 

 among them are the old Darwinian theory, the origin 

 of all modern theories and Weismann's more recent 

 theorv. 



