VARIATIONS, DUE TO REVERSION. 63 



sessed, at some time in the past ; then, there is an end 

 to Darwin's hypothesis, which is tenable, only upon 

 the supposition, that the progress displayed by such 

 species is new growth (i. e., new to the given species) 

 or new development; and upon the supposition that 

 there is no limit to such progress, or variation. 



Respecting the degeneration, which has taken 

 place in the past under nature, and the capacity, 

 ever resident in the deteriorated individuals, to re- 

 cover what they lost, Darwin says (p. 188, Origin of 

 Species) : 



" No doubt it is a very surprising fact, that charac- 

 ters should reappear, after having been lost for many, 

 perhaps, for hundreds, of generations. * * * In a 

 breed which has not been crossed, but in which both 

 parents have lost some characters which their progeni- 

 tor possessed, the tendency, whether strong or weak, 

 to reproduce the lost characters, might be, as was form- 

 erly remarked, for all that we can see to the contrary, 

 transmitted for almost any number of generations. 

 When a character, which has been lost in a breed, 

 reappears, after a great number of generations, the 

 most probable hypothesis is, not that the offspring 

 suddenly takes after an ancestor some hundreds of 

 generations distant, but that, in each successive gener- 

 ation, there has been a tendency to reproduce the 

 character in question, which, at last, under unknown 

 favorable conditions, gains an ascendancy." 



This power of reversion, as he says, is ever opera- 

 tive, and is only kept down by adverse conditions. 

 Each individual of a species would, were the condi- 

 tions propitious, develop all the positive characters, 

 known to any individual of its species. 



