From the Unconscious to the Conscious 



Let us return to Le Dantec's explanation of specific 

 form. Are we to admit that the conditions of chemical 

 equilibrium, which is its supposed basis, continually 

 change during the development of an animal, and change 

 in a given sense following a pre-determined direction 

 leading to the adult form ? So be it; but this is once 

 more to have recourse to the ' directing idea,' in other 

 words, to restore to physiology all the finality which it 

 claimed to discard. 



The tadpole has all the organs, the constitution, 

 and the mode of life of a fish. Suddenly, without change 

 of environment or mode of life, its conditions of chemical 

 equilibrium are about to alter. They will be modified 

 in such a manner, according to Le Dantec, that legs 

 will appear, that lungs will replace gills, that 

 the heart with two cavities will become one with 

 three cavities; in short, that the fish will become a 

 frog! 



Consider the medusa. Its successive larval forms are 

 so different from each other that they were long taken 

 for distinct animals. 



How is the genesis of these successive forms to be 

 explained by modifications in the chemical equili- 

 brium ? 



In these metamorphoses of embryonic life there is a 

 double problem. First the problem of the metamorphoses 

 themselves. How do they come about ? How do they 

 recall either the transitional forms of the evolutionary 

 ancestry, or the details of divergent larval adaptations ? 

 Where, and how, is the ineffaceable imprint of these 

 ancestral forms and adaptations preserved ? 



Then there is the problem of the individual expansion. 

 How is it that these changes do not interfere with its 

 reaching the definite adult form ? How is it that this 

 form is always attained, certainly and without fail ? If 

 we see nothing in the individual but a cellular complex, 

 the double problem cannot be solved. 



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