The Various Forms of Variability. 43 



further. If his assumption is once granted everything 

 else follows. On page 13 he again sums up his position. 

 He is concerned there to show that variations of every 

 kind can be increased and accumulated by selection not 

 only in the cultivated but in the wild condition. I fully 

 admit that Wallace has effected this proof in a masterly 

 and convincing manner. But we also require proof that 

 this increase and accumulation takes place ''to the amount 

 requisite'' for the origin of new species and subspecies; 

 and this proof Wallace neither brings forward nor 

 seeks. Instead of it, his book is full of instances of the 

 compound nature of cultivated and of wild species and 

 of their so-called elementary or subspecies ;^ but how 

 these have arisen we are not told. He has equally little 

 success in proving that races which have arisen by selec- 

 tion remain constant without further selection. 



Finally, we see that Wallace in his selection theory 

 starts from individual or ordinary variability and allows 

 no share in the process to single variations. He shows 

 that the hypothesis thus simplified effectively coordinates 

 systematic and biological facts, but he fails in proving 

 that as a matter of fact specific characters can really 

 arise by the selection of individual differences. 



§ 4. THE VARIOUS FORMS OF VARIABILITY. 



Nothing is more variable than the meaning of the 

 word variability. Many authors use this word in so 

 comprehensive a sense that one cannot understand what 

 they mean. (Fig. 8.) 



It is therefore important to distinguish as clearly as 

 possible between the various phenomena included under 



See for example pp. 77-78, 85-86, etc. 



