THE WONDERS OF LIFE 



sense of the word, is at the bottom merely a "phyletic 

 vital force." It is not made more acceptable by Nageli 

 when he builds up a subtle metaphysical system on it 

 and postulates a special "principle of isagitation." But 

 the idioplasm theory he connects with it is of some value, 

 since it goes more fully into the differentiation of the 

 cell-plasm into two physiologically different parts — the 

 idioplasm of the hereditary matter and the trophoplasm 

 as nutritive matter of the cell. 



The vitalist and teleological idea of an internal prin- 

 ciple of evolution, that determines the origin of animal 

 and plant species independently of the environment and 

 its conditions, is not only found in the "mechanical- 

 physiological" theory of Nageli, but also in sev^eral 

 other attempts to explain the agencies of the transfor- 

 mation of species. All these efforts are welcomed by 

 the academic philosophers with their Kantist dualism 

 (mechanicism on the right, teleology on the left), and 

 who are particularly anxious to save the supernatural 

 element, Reinke's "cosmic intelligence," or the wisdom 

 of the Creator, or the divine creative thought. All these 

 dualistic and teleological efforts have the same fault: 

 they overlook, or fail to appreciate properly, the im- 

 mense influence of the environment on the shaping and 

 modification of organisms. When, moreover, they deny 

 progressive heredity and its connection with functional 

 adaptation, they lose the chief factor in transformation. 

 This applies also to the theory of germ-plasm. 



The desire to penetrate deeper into the mysterious 

 processes that take place in the plasm in the physio- 

 logical activities of heredity and adaptation has led to 

 the formulation of a number of molecular theories. The 

 chief of these are the pangenesis theory of Darwin (1878), 

 my own perigenesis theory (1876), the idioplasm theory 

 of Nageli (1884), the germ-plasm theory of Weismann 

 (1885), the mutation theory of De Bries, etc. As I have 



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