188 THE STORY OF LIFE'S MECHANISM. 



reproduction is a device adopted for bringing 

 out such congenital variations. 



INHERITANCE OF VARIATIONS. 



The reason why congenital variations are needed 

 for the evolution of the living machine is clear 

 enough. Evanescent variations can have no effect 

 upon this machine, for they would disappear with 

 the individual in which they appeared. In order 

 that they should have any influence in the pro- 

 cess of machine building they must be permanent 

 ones ; or, in other words, they must be inherited 

 from generation to generation. Only as such 

 variations are transmitted by heredity can they 

 be added to the structure of the developing 

 machine. Therefore we must ask whether the 

 variations are inherited. 



In regard to the congenital variations there 

 can be no difficulty. The very fact that they 

 are congenital shows us that they have been pro- 

 duced by variations in the germ plasm, and as 

 such they must be transmitted, not only to the 

 next generation, but to all following generations, 

 until the germ plasm becomes again modified. 

 This germ plasm is handed on from generation 

 to generation with all its variations, and hence 

 the variations will be added permanently to the 

 machine. Congenital variations are thus a means 

 for permanently modifying the organism, and by 

 their agency must we in large measure believe 

 that evolution through the ages has taken place. 



With the acquired variations the matter stands 

 quite differently. We can readily understand 



