Three Types of TJieory 



character the principles of organic selection and social 

 transmission. These two principles, which rest upon facts 

 for their validity, are in this theory given a place and a 

 relation to the other factors of the theory of descent, and 

 also to each other, not given to them in any other general 

 theory. It is accordingly quite within the general usage 

 of biologists to give such a theory a name. The term 

 * orthoplasy ' has been suggested above as such a desig- 

 nation for the theory a term which from its derivation 

 (Greek opOds straight, and 7rXa<m, a moulding seen in the 



3 



Theory of Neo-Darwinism or Weismannism. LL', line of evolution ; i, 2, etc., 

 successive generations by physical heredity; cm, cm', etc., congenital mean; 

 v, v' , variations (congenital). Evolution is by natural selection of variations 

 added to the congenital mean from generation to generation. 



English vf QT& plastic) appropriately designates a view which 

 mainly concerns itself with the factors at work in the 

 determination or direction of the movement of evolution. 



The relation of this theory to other current general 

 views is indicated here and there in the preceding pages. 

 Many of the papers here reprinted were written in the 

 first instance to show that this theory is free from objec- 

 tions urged to Neo-Lamarckism and Neo-Darwinism ; and 

 it has been pointed out in what way orthoplasy finds itself 

 ' orientated ' with respect to the less general truths on 



