APPENDIX. n 



ceeding in tiie direction of adaptive growth, it is re- 

 markable that the same was not made l<mg ago by 

 scHne one or other of the many who have thought and 

 written on selectitm and evolution. 



Allusions to a connexion between the direction 

 of \-ariation and the selective processes are to be found, 

 but they remained mmoticed or undeveloped. I have 

 been able to find at least two such observations, but 

 would not wish to assert that there are not more of 

 tham hidden somewhere in the literature of the subject. 

 One of them is old and CMnes from Fritz Muller. It 

 was appended by his brother Hermann as a '■Sujq)le- 

 mentary Remark" to his book Die Befruchiung der 

 Blumen durch Iitsectcn (1873) and is dated Novem- 

 ber 24, 1872. We read there: "My brother Fritz 

 Muller ccHimiimicates to me in a letter which reached 

 my hands only after the bulk of the present work had 

 passed through the press, the f (dlowing law discovered 

 by him, which materially facilitates the explanation by 

 natural selection of the pronounced characters of 

 sharply distinguished species : 'The moment a choice 

 in a definite directicm is made in a variable species, 

 prt^iessive modification from generation to genera- 

 tion in the same direction will set in as the result of 

 this choice, wholly apart from the influence of ex- 

 ternal conditions. Transformation into new forms is 

 thus greatly facilitated and accelerated.' " 



The facts on which F. Muller based the enunciation 

 of his law, are the results of several experiments with 

 plants, the numbers of whose grains (maize) , or stjles, 

 or flowering leaves, were^ by the exercise of choice in 

 the cultivation, made to change in definite directions. 

 Accurately viewed their significance is the same as 

 that of numerous other cases of artificial selection, for 



