VAKIATIONS, DUE TO REVERSION. 11 



generations, in the case of crossed breeds, and during 

 thousands of generations, in the case of pure breeds, 

 written as it were in invisible ink, yet ready, at any 

 time, to be evolved under the requisite conditions." 



" What these conditions are, we do not in many 

 cases at all know. But, the act of crossing, in itself, 

 apparently from causing some disturbance in the or- 

 ganization, certainly gives a strong tendency to the re- 

 appearance of long-lost characters, both corporeal and 

 mental, independently of those derived from the cross." 



The purpose in quoting this, and other remarks of 

 Darwin, upon the subject of long-lost characters, is, to 

 show the wide-spread operation of Reversion, and its 

 competency to cover all the variations adduced by 

 Darwin. Having thus furnished full warrant for the 

 assumption of Reversion as the sole cause of all posi- 

 tive variations, or improvements, we shall also en- 

 lighten him as to what those mysterious conditions 

 are, of which he speaks, and as to what that curious 

 " some disturbance in the organization," is. 



On page 113, Vol. ii, Animals and Plants, &c, he 

 says: 



" But in all cases " (of crossing different breeds) 

 "there will be, during many subsequent generations, 

 more or less liability to reversion. * * * In con- 

 sidering the final result of the commingling of two or 

 more breeds, we must not forget that the act of cross- 

 ing in itself tends to bring back long-lost characters, 

 not proper to the immediate parent-forms." 



Again, on page 2 1 2, Vol. ii, Animals and Plants, &c, 

 he speaks of 



" The excessive variability of the crossed offspring 

 due to the principle of reversion." 



