CHAPTER XV. 



CONDITIONS OF DEVELOPMENT. DEATH. 



CONCLUSION. 



The different methods of development of various 

 organisms cannot be accounted for by difference 

 in the chemical composition of the germs, nor by 

 difference in their cellular structure. We must recog- 

 nise some general property of living matter, by virtue 

 of which the individual and racial development of 

 organisms takes place. We can only express it 

 as that which is the basis of nervous co-ordination 

 and which makes all nervous activity possible. It 

 is something which is not destroyed by the division 

 of an organism, nor by the fusion of two organisms 

 into one. The latent potentialities of the two 

 organisms, which are based upon this property, may 

 be mixed in a great variety of combinations, — 

 combinations which are, however, dependent upon 

 the stimuli to which the organism is subjected during 

 its development. In no case can we recognise this 

 property of development as acting independently 



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