78 APPENDIX. 



example, that of the long-tailed Japanese cock which 

 was laid at the foundation of the theory in the teart, 

 although the numerical fonn of the observation gives 

 more precision and distinctness to the reasoning based 

 on them, than is to be observed in cases where we 

 speak of characters as being simply "longer" or 

 "shorter." 



F. Miiller's opinion regarding the increase of char- 

 acters by-election is expressed as follows: "The 

 simplest explanation of these facts appears to be that 

 every species possesses the faculty of varying within 

 certain limits; the crossing of different individuals, 

 so long as no choice is effected in a definite direction, 

 n^intains the mean round which the oscillations take 

 place at the same points, and consequently the ex- 

 tremes also remain unaltered. If, however, one side 

 is preferred by natural or artificial selection, the mean 

 is shifted in the direction of this side and according^ 

 the extreme forms are also displaced towards that sid^ 

 going now beyond the original limit However, this 

 explanation does not satisfy me in all cases." 



It is not known to me that F. Miiller ever returned 

 to this conception subsequently to the jtsi 1872 or 

 gave further developments of the same, nor have I 

 been able to discover that it has been mentioned by 

 other writers or incorporated in previous notions re- 

 garding selection. 



The second naturalist who has approached the fun- 

 damental idea of my doctrine of germinal selection, is 

 a more recent writer. I refer to the EJiglish botanist 

 ThisdtOTtDyer, a scientist whose occasional utterances 

 on the general questions of hvAogy have more than 

 once evoked my sympathetic approval In an artide, 

 "Variation and Specific Stability," which appeared in 



