THE GROWTH OF GROUPS 169 



searching for the same thing and may be able to help one 

 another. 



In the last chapter we saw that mutants appeared in 

 response to physical change such as heat and drought. 

 But we cannot feel satisfied that such stimuli are of great 

 importance in the production of the mutants. They are 

 like an impulse that sets something moving, something 

 lying ready to be released. That something is hidden in 

 the nature of the organism. 



All we know is that each kind of organism is in the 

 habit of throwing off other kinds from time to time. The 

 beetle decemlineata throws off pallida and tortuosa and 

 others. The evening primrose produces a number of 

 recognizable kinds. It may be assumed that the human 

 race produces these peculiar mental types, such as are 

 recognized by the alienist, in like manner on various 

 occasions. 



This chapter is not quite in keeping with the others ; 

 its chief purpose is to show that the Mutation Theory is 

 of importance in pathology. 



