1 86 Orthoplasy 



§ 4. Three Types of Theory 



Any general theory of determinate and divergent evo- 

 lution — in short any theory of descent, whether of a 

 character or of an organism, of mind or of body — has a 

 complexion derived from the composition of the factors it 

 employs or assumes. The theory which exclusively em- 

 ploys natural selection is called Neo-Darwinism or Weis- 

 mannism ; the theory which gives use-inheritance a large 

 place, whether laying greater or less stress upon natural 

 selection and other factors as subordinate, are called 

 Lamarckism or Lamarckianism. Vitalism takes on a 

 variety of forms, which have specific names, according as 

 their respective holders make prominent specific modes of 

 operation in which the life forces work themselves out 

 — as the ' self -development ' theory, the auto-regulation 

 (Delage) theory, the orthogenesis theory, the theories of 

 bathmism, growth-energy, etc. This is certainly both 

 legitimate and convenient — to suggest a term to desig- 

 nate a theory which, in its main hypothesis or in its 

 manner of grouping the subsidiary hypotheses, presents 

 a distinguishable and discussable whole.^ 



The theory which is expounded in these pages presents 

 two principles which, both in the formation given to them 

 and in the r61e assigned to them in the theory of descent, 

 mark it as having such a distinguishable and discussable 



^ Professor Conn, speaking of the theories of isolation and organic selection, 

 says : * There can be no question that these two theories are important con- 

 tributions to the problem of organic evolution. In regard to the disputed 

 question of whether they are a part of natural selection and therefore included 

 in Darwinism we need attempt no decision. They certainly represent aspects 

 of the problem not recognized until recently, and may therefore be looked 

 upon as actual contributions to our knowledge of evolution ' ( The Method of 

 Evolution, p. 333;. 



