208 THE NATURE AND ORIGIN OF LIFE 



of equilibrium, this mysterious question of the heredity 

 of acquired characters takes an extremely simple aspect. 

 Observation in general proves that for a character to be 

 fixed definitively in the heredity of a race it has to be ac- 

 quired successively during a very great number of genera- 

 tions. 



Rudimentary Organs 



When a character has been acquired by a race during a 

 great number of generations under the influence of a factor 

 B, it is transmitted along the whole line of descent. There 

 it is preserved and there it develops so much the more as 

 the factor B persists the longer among the life-conditions 

 of the species. 



But if, at the end of a certain time, the factor B disap- 

 pears from the education of the adult, the character, really 

 and profoundly acquired, will not itself disappear on that 

 account. It always manifests itself in the development of 

 the embryo under the influence of conditions which are 

 different from those which would make it function in the 

 adult. Only, since it is no longer kept up by functional 

 assimilation, it preserves at the end of embryo development 

 the volume which it had acquired during this first portion 

 of life and even begins a regression. But it is very difficult 

 for it to disappear completely in the descent of the species 

 because, since the conditions of embryo-development are 

 altogether different from those of the functioning of the adult, 

 the fact that the organ does not function in the adult will 

 not prevent it from functioning for another reason in the 

 embryo. 



Thus the appendix of our coecum is developed in the 

 intestine during our sojourn in our mother's womb, after 

 which, not being used in our adult mechanism, it per- 



