CHAPTER XVII. 



SUMMARY OF MORPHOLOGICAL DEVELOPMENT. 



« 



§ 262. That any formula should be capable of expressing 

 a common character in the shapes of things so unlike as a 

 tree and a cow, a flower and a centipede, is a remarkable 

 fact ; and is a fact which affords strong prima facie evidence 

 of truth. For in proportion to the diversity and multiplicity 

 of the cases to which any statement applies, is the probability 

 that it sets forth the essential relations. Those connexions 

 which remain constant under all varieties of manifestation, 

 are most likely to be the causal connexions. 



Still higher will appear the likelihood of an alleged law of 

 organic form possessing so great a comprehensiveness, when 

 we remember that on the hypothesis of Evolution, there must 

 exist between all organisms and their environments, certain 

 congruities expressible in terms of their actions and reactions. 

 The forces being, on this hypothesis, the causes of the forms, 

 it is inferable, a priori, that the forms must admit of generali- 

 zation in terms of the forces ; and hence, such a generalization 

 arrived at a posteriori, gains the further probability due to 

 fulfilment of anticipation. 



Nearer yet to certainty seems the conclusion thus reached, 

 on finding that it does but assert in their special manifesta- 

 tions, the laws of Evolution in general — the laws of that 

 universal re-distribution of matter and motion which hold 



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