EVOLUTION 375 



appearance of the successive forms of life during the 

 inorganic evolution of the earth forms a theory of organic 

 evolution. If the theory be so satisfactory that it resumes 

 in some very simple statement the whole range of organic 

 change, we term it the law of organic evolution. 



S 3. — Bathmic Evolution 



Now the physical evolutionists take almost invariably 

 as the antecedent of any given terrestrial stage a purely 

 physical set of phenomena ; they give no sensible weight 

 to the action of organic life on its environment. Possibly 

 they ought occasionally to give more weight, but doubtless 

 in the biggest features of inorganic evolution — changes of 

 temperature, and the formation of mountains and oceans — 

 they are on the right lines. Now in dealing with organic 

 evolution we might proceed in the same way and limit 

 the changes in organic forms to the condition of ante- 

 cedent organic forms. We might assert that one type of 

 life has evolved from another owing to inherent properties 

 in the earlier living forms themselves. There is nothing 

 more (or less) unscientific in using an " inherent growth- 

 force " to " explain " the secular changes in living forms 

 than in using a force of gravitation inherent in " matter " 

 to " explain " the development of planetary systems from 

 nebulae. The ultimate action of vital units in each 

 other's presence would be no more nor less of a mystery 

 than the ultimate action of material units. Such an 

 evolution has been termed bathmic evolution} The real 

 objection to bathmic evolution lies not in any a priori 

 reason against an " inherent growth-force," but to the 

 obvious historical fact that such a " force " has been used 

 to cover all sorts of obscure reasoning and even sheer 



^ Presumably from Greek ^adfxis with the sense of dasaL The term as 

 well as the notion of an "inherent growth-force" compelling the forms of 

 life to vary in a definite manner is due to the American Neo-Lamarckians. 

 Thus the growth indicated in the latter phrase does not refer in the first 

 place to an individual growth, but to a racial change of type owing to 

 successive generations having a tendency (due ultimately to the " inherent 

 growth-force ") to vary progressively. 



