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EEV. J. T. GULICK ON DIVERGENT EVOLUTION 



CHAPTER I. 



The Effects of Selection and Independent G-eneeation 

 Contrasted. 



In as far as any theory of evolution fails of giving an explanation 

 of divergence of character, in so far it fails of explaining the origin 

 of species. This is the crucial test which must decide the strength 

 or weakness of every theory that is brought forward to account 

 for the derivation of many species from one original species. A 

 satisfactory theory will not only point out the conditions on 

 which divergence depends, but will show that these conditions 

 are the natural result of causes that are already recognized by 

 science as having influence in the organic world, or tbat are now 

 shown to have such influence. 



In the present chapter I shall present some reasons for believing 

 that neither " Natural Selection," nor Sexual Selection," nor 

 *' the Advantage of Divergence of Character," nor " Difi^erence 

 of External Conditions," nor all these taken together, nor any 

 form of Selection that may be hereafter discovered, is sufficient 

 to account for Divergence of Character, but that another factor 

 of equal if not superior importance must be recognized. In sub- 

 sequent chapters I shall try to trace the causes on which this 

 additional factor depends, and to indicate as far as possible the 

 laws and relations under which they appear. 



Divergent Evolution not explained by Natural 

 Selection. 



Natural Selection is the exclusive generation of certain forms 

 through the failure to live and propagate of other kinds that are 

 less adapted to the environment. 



In the case of the breeder, no selection avails anything that 

 does not result in some degree of exclusion. In the case of 

 natural selection, where we are not considering ineff'ectual inten- 

 tions, the selection is measured by the exclusion. Where there 

 is no exclusion, there is no selection, and where the exclusion is 

 great the selection is severe. Moreover, it is self-evident that there 

 can be no crossing between the best fitted that survive and propa- 

 gate, and the least fitted that perish without propagating. To this 

 extent, therefore, the prevention of crossing is complete. And 

 further, it is evident that those whose meagre fitness gives them 

 but little opportunity for propagating will have a correspondingly 



