78 THE ORIGIN AND EVOLUTION OF LIFE 



other organs, it is possible that hormones and chalones arising 

 from the various cellular activities of the body itself may act 

 upon the physicochemical elements in the germ-cells which 

 correspond potentially to the tissues from which these hor- 

 mones and chalones are derived. Cunningham was a strong 

 believer in the Lamarckian explanation (see p. xiii) of evolu- 

 tion, and his heredity hypothesis was designed to suggest a 

 means by which the modifications of the body due to environ- 

 mental and developmental conditions could so modify the 

 corresponding tissues and physicochemical constitution of the 

 chromatin in the germ-cells as to become hereditary and re- 

 appear in subsequent generations. 



Physicochemical Differentiation 



As the result of recent investigations of cancer, Loeb^ comes 

 to the following conclusions: 



"We must assume that every individual of a certain species 

 differs in a definite chemical way from every other of that 

 species, and that in its chemical constitution an animal of one 

 species differs still more from an animal of another. Every 

 cell of the body has a chemical character in common with ev- 

 ery other cell of that body and also in common with the body 

 fluids; and this particular chemical group differs from that of 

 every other individual of the species and to a still greater de- 

 gree from that of any individual of another group or species. 

 Thus it happens that cells belonging to the same organism are 

 adapted to all the other cells of that organism and also to the 

 body fluids. . . . 



"It has been possible to demonstrate by experimental 

 methods that there are fine chemical differences not only be- 

 tween different species and between different individuals of 



^ Loeb, Leo, 1916, pp. 209-226. 



