4 Introductory Remarks 



organism as a whole is in his opinion not produced by 

 the same forces and he considers it impossible and 

 hopeless to investigate the "design." This attitude 

 of Bernard would be incomprehensible were it not for 

 the fact that, when he made these statements, the 

 phenomena of specificity, the physiology of develop- 

 ment and regeneration, the Mendelian laws of heredity, 

 the animal tropisms and their bearing on the theory 

 of adaptation were unknown. 



This explanation of Bernard's attitude is apparently 

 contradicted by the fact that Driesch 1 and v. Uexkull," 

 both brilliant biologists, occupy today a standpoint 

 not very different from that of Claude Bernard. Driesch 

 assumes that there is an Aristotelian "entelechy" 

 acting as directing guide in each organism; and 

 v. Uexkull suggests a kind of Platonic "idea" as a 

 peculiar characteristic of life which accounts for the 

 purposeful character of the organism. 



v. Uexkull supposes as did Claude Bernard and as 

 does Driesch that in an organism or an egg the ulti- 

 mate processes are purely physicochemical. In an 

 egg these processes are guided into definite parts 

 of the future embryo by the Mendelian factors of 

 heredity — the so-called genes. These genes he compares 

 to the foremen for the different types of work to be 



1 Driesch, H., The Science and Philosophy of the Organism. 2 vols. 

 The Gifford Lectures, 1907 and 1908. 



a v. Uexkull, J., Bausteine zu einer biologischen Weltanschauung. 

 Munchen, 1913. 



