THEORIES OF HEREDITY 111 



unanimously. Certain naturalists refuse to believe 

 that the shape of the body and the properties of its 

 different parts depend merely upon the one particle 

 of the cell in which they originate. In their opinion, 

 they depend upon "the whole," they result from the 

 co-operative and competitive workings of all the ele- 

 ments, cells, tissues, organs, all of which live their 

 individual life and finally produce a complex which 

 apparently reveals a pre-established harmony, but 

 which is due in reality to independent phenomena. 

 This conception first originated with Descartes, but it 

 has been so deeply modified that hardly anything is 

 left of the original hypothesis, and that, under its 

 present name of "organicism," it can be considered as 

 a truly modern theory. 



According to the former theory known as the mi- 

 cromerist theory, the hypothetical particles of proto- 

 plasm are all identical in every organ and in every 

 part of an organism; the differences between them 

 result from the way in which they are grouped, from 

 the forces of attraction which influence them and 

 from their special motions. Spencer who was the 

 first to formulate a theory based upon the existence 

 of protoplasmic particles gives the following explana- 

 tion of the process: The small particles of living 

 matter, which he designates as physiological units, are 

 intermediary between the chemical units, or molecules, 

 and the morphological units, or cells; they are made 



