150 Permanence and Evohition. 



porters of natural selection," because "on this 

 theory the chances are almost indefinitely 

 against the independent accidental preservation 

 of two similar series of minute variations re- 

 sulting in the independent development of two 

 closely similar forms,"* and he considers that 

 any other form 'of the evolution hypothesis is 

 not affected by the argument ; but it is evident 

 that the mind, when it is once accustomed to 

 consider similarity as arising independently of 

 descent, is likely to have its faith shaken as 

 to the hypothesis in any form. 



The same may be said of Mivart's remarks 

 on specific variability. He points out with 

 justice that if species had been formed by 

 gradual transition, more traces must have re- 

 mained of the intermediate steps, and thinks 

 that this difficulty can be avoided by making 

 the transition sudden, in support of which he 

 gives instances like that of the black-shouldered 



* This, however, seems doubtful. See p. 106. 



