NATURAL SELECTION, ETC. 95 



triumphs of our age in physical science have consisted 

 in tracing connections where none were known before, 

 in reducing heterogeneous phenomena to a common 

 cause or origin, in a manner quite analogous to that 

 of the reduction of supposed independently originated 

 species to a common ultimate origin — thus, and in 

 various other ways, largely and legitimately extending 

 the domain of secondary causes. Surely the scientific 

 mind of an age which contemplates the solar system 

 as evolved from a common revolving fluid mass — 

 which, through experimental research, has come to re- 

 gard light, heat, electricity, magnetism, chemical affin- 

 ity, and mechanical power as varieties or derivative 

 and convertible forms of one force, instead of inde- 

 pendent species — which has brought the so-called ele- 

 mentary kinds of matter, such as the metals, into 

 kindred groups, and pertinently raised the question, 

 whether the members of each group may not be mere 

 varieties of one species — and which speculates steadily 

 in the direction of the ultimate unity of matter, of a 

 sort of prototype or simple element which may be to 

 the ordinary species of matter what the Protozoa or 

 what the component cells of an organism are to the 

 higher sorts of animals and plants — the mind of such 

 an age cannot be expected to let the old belief about 

 species pass unquestioned. It will raise the question, 

 how the diverse sorts of plants and animals came to 

 be as they are and where they are, and will allow that 

 the whole inquiry transcends its powers only when 

 all endeavors have failed. Granting the origin to be 

 supernatural, or miraculous even, will not arrest the 

 inquiry. All real origination, the philosophers wiD 



