ORIGIX OF LIFE, SEX, SPECIES, ETC. 205 



which complementariness of their shapes and sizes 

 suggest. In this interlocked position, they would 

 offer a much more effective resistance to disturb- 

 ance or separation by external influences than 

 when each kind is concentrated by itself. Various 

 kinds of so-called chemical affinities might be ex- 

 plained on this principle, and it is immaterial 

 whether for the purpose of such explanation it is 

 assumed that the forms of particles are derived from 

 the forces inherent in them, or vice versa. 



Each fresh impulse imparted from moment to 

 moment by the general commotion must disturb, 

 and therefore delay, the concentration in orderly 

 masses which the proper motions of the particles 

 of each substance tend to produce, as above ex- 

 plained. Since the actual motions of any particle 

 are the results of both the tendency to concentrate 

 and of the hindrance which this undergoes, as above 

 explained, therefore can the proper motions not 

 impart a direct but only an indirect impulse towards 

 concentration of like with like and separation from 

 unlike. 



Since masses composed of like particles are called 

 pure, and those which are otherwise are called 

 impure, therefore it follows that the occurrence in 

 the natural course of events of perfectly pure sub- 

 stances must be exceedingly rare, and therefore 

 that most masses of matter possess a degree of 

 impurity which leaves a large margin for improve- 

 ment in purity, and that the degree of this purity 



