52 Heredity and Social Progress 



are many instances, for regeneration is a com- 

 mon phenomenon among lower animals, and 

 is in some degree found in all organisms. 

 When an animal replaces a lost limb, a pro- 

 cess of reduction takes place by which the 

 cells adjoining the lost part are brought back 

 to the degree of simplicity of the original cells 

 before the growth of the part began. Reduc- 

 tion always precedes regeneration. If the 

 changes in the cells which create the new 

 part could be observed, reductions would be 

 found similar to those that take place when 

 polar bodies are expelled. In reproduction, 

 cells are simplified by the throwing off of 

 polar bodies, and subsequently their natural 

 growth re-creates the lost part. Reproduction 

 and the regeneration of lost parts are not differ- 

 ent processes, but spring from the same forces 

 acting under slightly different conditions. 



Carrying this reasoning a step farther, an- 

 other group of facts may be correlated with 

 those just given. Emotions are the psychic 

 expression of certain bodily changes, and 

 represent the effects on organisms of the per- 

 ception of adverse elements in the environ- 



