CHAPTER VI. 



THEORY OF DEVELOPMENT AND HEREDITY ILLUS- 

 TRATED AMONG PROTOZOA. 



After we have made full allowance for the 

 action of stimuli on an organism during the period 

 of its growth from inception to maturity, and have 

 allowed the great importance and necessity of this 

 action to the developing organism, there still remains 

 unaccounted for a sum of forces which are innate 

 in the organism, and which determine its essential 

 nature and specific character. The question arises, 

 what is the origin of those innate forces which 

 determine whether a developing organism will be 

 a horse or a dog .' If we accept evolution, even 

 in its simplest form, we mus't believe that the 

 peculiar co-ordination of forces necessary to produce 

 a horse, could not have existed before the appear- 

 ance of vertebrates on the earth. If the conti- 

 nuity of life remained unbroken, the co-ordination 

 of forces which produce the horse, must have been 

 gradually acquired by living matter in the long 



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