58 THE MYSTERY OF LIFE. 



derived from a pre-existing living thing. The 

 formation of tissue has been attributed to 

 " vacuolation " and " differentiation," and these 

 polysyllables have lately been superseded by 

 the still more vague terms " subtle influences," 

 and " external conditions," and " sundry circum- 

 stances." And it has been affirmed that to " the 

 primitive properties of the molecules" and 

 " natural selection " may be referred all the 

 varying forms and structures known to us as 

 well as all the phenomena of the living world. 

 But such terms explain nothing. By their use 

 further enquiry is discouraged, and the mind 

 bent upon investigating the secrets of nature is 

 misled at the very outset. Can any one of 

 these very pretentious phrases be resolved into 

 anything more than the statement of a fact or 

 facts in the form and language of an explana- 

 tion ? Natural selection is the formation of 

 species, and species are produced by natural 

 selection. Crystallisation is the formation of 

 crystals, and crystals are produced by the opera- 

 tion of crystallisation. Tissues are formed by 

 differentiation, and differentiation is the forma- 

 tion of tissues ; and so on. But whether forma- 

 tion be attributed to " subtle influences " and 



