NATURE AND CAUSES OF VARIATION 27 



with that from another, we will get what corresponds 

 to a new generation. The individuals of this genera- 

 tion will obviously differ from either of their parents; 

 but what is more, they will differ amongst themselves, 

 for some may contain three whites, others four or five, 

 or two, and so on. 



This is something like what we conceive to be going 

 on in heredity. We must not compare bi-parental 

 inheritance to an intimate blend of two substances, 

 which would cause any sample of the mixture to be the 

 same as any other sample ; for we know that the 

 mechanism of heredity is not of this nature. The 

 mechanism gives large opportunity for different com- 

 binations to result from the mating of the same two 

 parents. We shall consider later the laws according 

 to which these re-combinations occur. 



In the above example we supposed no new kinds 

 of marbles. Only the combinations of the different 

 colours were new. In heredity it is believed that most 

 inborn variations are due to re-combinations of pre- 

 viously existing characters that most of our new houses 

 are built of old bricks. It may well be that Shakespeare 

 or Darwin, Goethe or Napoleon, were nothing more 

 than very happy combinations of the traits of their 

 ancestors. Goethe himself recognised this when he 

 wrote the well-known lines : 



" Vom Vater hab' ich die Statur 

 Des Lebens ernstes Fiihren, 

 Vom Mutterchen die Frohnatur 

 Und Lust zu f abulieren. " * 



But before we can have new combinations we must 

 start with actual differences. Our experiment with the 

 marbles would have shown nothing, if all the marbles 

 had been white. How do the real differences arise ? 

 There are occasions in which something manifestly 



1 " From nay father I inherit my stature 

 And earnest conduct of life, 

 From my mother my cheerful disposition 

 And my love for the romantic." 



