274 Darwin, and after Darwin. 



involves a grave error of reasoning to suppose that 

 this question can be answered deductively from the 

 theory of natural selection itself, as I shall show at 

 some length in the next volume. 



A still more extravagant, and a still more un- 

 accountable fallacy is the one which represents it as 

 following deductively from the theory of natural 

 selection itself, that all hereditary characters are 

 " necessarily " due to natural selection. In other 

 words, not only all adaptive, but likewise all non- 

 adaptive hereditary characters, it is said, must be due 

 to natural selection. For non-adaptive characters are 

 taken to be due to "correlation of growth," in con- 

 nexion with some of the adaptive ones natural 

 selection being thus the indirect means of producing 

 the former wherever they may occur, on account of its 

 being the direct and the only means of producing the 

 latter. Thus it is deduced from the theory of natural 

 selection itself, ist, that the principle of natural 

 selection is the only possible cause of adaptive modifi- 

 cation : 2nd, that non-adaptive modifications can only 

 occur in the race as correlated appendages to the 

 adaptive : 3rd, that, consequently, natural selection is 

 the only possible cause of modification, whether 

 adaptive or non-adaptive. Here again, therefore, we 

 must observe that none of these sweeping general- 

 izations can possibly be justified by deductive reasoning 

 from the theory of natural selection itself. Any attempt 

 at such deductive reasoning must necessarily end in 

 circular reasoning, as I shall likewise show in the 



the following paragraphs, therefore, " adaptations," " adaptive modifica- 

 tions," &c., refer exclusively to such as are hereditary, i. e. phyletic. 



