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vain for the common ancestor of differentiated species 

 The genealogical tree is all branches and no stem The 

 proposal to treat man as an exception fore-doomed If 

 Divine intelligence be needful to account for man, it is 

 needful to account for inferior species Wallace regards 

 man as exempt from the great law of organic change 

 Darwin's position safer as an evolutionist, in boldly in- 

 cluding him Spencer stakes his theory on the adequacy 

 of dynamic law to account for the whole He condemns 

 Prof. Owen's ' ' continuous unknown process " No more 

 comprehensible by science than ' ' special creations " The 

 causes recognized by Mr. Spencer are (a) an innate ten- 

 dency or polarity in the physiological units, and (6) the 

 play of incident forces The unit has an internal system 

 of forces equilibrated in harmony with ancestral form, 

 the incident forces disturb this equilibrium In regaining 

 equilibrium the structure is modified The explanation 

 carries us back to the atom and its environment The 

 differentiation of sex Differentiation of structure due 

 altogether to environment Physiological unit dethroned 

 How account for the diverse action of the same en- 

 vironment ? Mr. Spencer gives two conflicting answers 

 Evolution cannot show in any comprehensible way the 

 mode of operation of the causes producing variety of forms 

 The dynamic hypothesis furnishes basis for theory dif- 

 ferent from " natural selection " Similarity of incident 

 forces should produce similarity of structure The verte- 

 brate structure may be result of similarity of causes and 

 not the outcome of identity of descent In Darwinian 

 theory the " incident forces " play a part that is negative 

 The removal of the less fit will not account for the pro- 

 duction of the fittest At bottom, the question is the pro- 

 duction and continuance of any The growth of a single 

 germ cannot be accounted for on the dynamic theory No 

 vital activity can be explained wholly by knowledge of 

 dynamic law A cause continually operative not to be 

 confounded with physical force Its truest representation 

 the energy of self-conscious mind, . . . 187 



