i8 Darwin, and after Darwin. 



shown, by saying that the one sex is anabolic and the 

 other katabolic ? In so far as these verbal statements 

 serve to express what is said to be a general fact 

 namely, that the female sexual elements are less 

 mobile than the male they merely serve to re-state 

 this general fact in terminology which, as the authors 

 themselves observe, is " unquestionably ugly." But 

 in so far as any question of origin or causality is con- 

 cerned, it appears to me that there is absolutely no 

 meaning in such statements. They belong to the 

 order of merely formal explanations, as when it is said 

 that the toxic qualities of morphia are due to this 

 drug possessing a soporific character.' 



Much the same, in my opinion, has to be said of 

 the Rev. G. Henslow's theory of the origin of species 

 by what he terms "self-adaptation." Stated briefly 

 his view is that there is no sufficient evidence of 

 natural selection as a vera causa, while there is very 

 abundant evidence of adjustments occurring without 

 it, first in individual organisms, and next, by inherit- 

 ance of acquired characters, in species. Now, much 

 that he says in criticism of the selection theory is of 

 considerable interest as such ; but when we pass 

 from the critical to the constructive portions of his 

 books and papers, we again meet with the want of 

 clearness in thought between a statement of facts 

 in terms of a proposition, and an explanation of 

 them in those of causality. Indeed, I understand 

 from private correspondence, that Mr. Henslow him- 

 self admits the validity of this criticism ; for in 

 answer to my questions, " How does Self-adapta- 

 tion work in each case, and why should protoplasm 

 be able to adapt itself into the millions of diverse 



