CHAPTER IV 

 THE LAMARCKIAN DOCTRINE 



Adaptation The main problem of heredity Theories of evolution The 

 Lamarckian hypothesis The Darwinian hypothesis The incompatibility of 

 the two Evidence against the former The most decisive proof of all Cor- 

 relation Diseases Maternal impressions Telegony. 



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86. f | ^O the student of heredity and evolution, who not only 

 gathers facts but strives to interpret them by ascertain- 

 ing their causal relations one to another, the cardinal 

 fact of life may be said to be the close adaptation of every species 

 to its environment, and the equally close co-adaptation of the 

 organs, tissues, cells, and functions of the normal individual to one 

 another. Thus the normal man, the normal ant, and the normal 

 oak are closely fitted during all stages of development to the con- 

 ditions of their surroundings, and could exist in no other. Within 

 plant and animal bodies, with rare and uncertain exceptions, every 

 structure and function, no matter how vast their multitude and com- 

 plexity nor how great the changes undergone during development, 

 works in exquisite co-adaptation with all its neighbours. Hardly one 

 of all these structures, whether useful in preserving the individual 

 life, or sexually ornamental and therefore useful in preserving the 

 species, whether functionally active or vestigial, but serves, or has 

 served, or will serve during the life of the individual the great 

 purpose of adaptation, the great purpose of enabling the individual 

 to survive and transmit his germ-plasm to offspring. Nearly one 

 and all, their existence has or had no significance other than 

 utility to the individual or to the race. So surely as we learn 

 much about a structure, almost so surely do we discover its function, 

 its utility in the past or the present of the race, or the past or 

 the present or the future of the individual. It is impossible to use 

 language too emphatic on the necessity to the student of heredity 

 and evolution of bearing constantly in mind this all-important 

 truth of adaptation. Its wonderful completeness has been denied, 

 but only, I think, when people, even scientific men, have founded 

 their thinking on exceptions instead of the rule, and even then 



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