GENERAL RELATIONS IN INHERITANCE 297 



In making the combination present in any individual a 

 large proportion of the genes present in any ancestor of an 

 earlier generation is excluded. Indeed all genes from some 

 of the ancestral individuals may be excluded. So for example 

 in the diagram of figure 62, there are in the individual of 

 generation IV no genes of individuals 2, 3 and 5 of genera- 

 tion I. 



The different combinations of the genes of the ancestral 

 generations that are present in the different individuals of 

 any given generation of course result in many different com- 

 binations of characteristics. In this way any of the genes, 

 with the corresponding characteristics, that were scattered 

 through many different individuals in past generations may 

 be brought together in one individual. 



A hypothetical illustration of the possibilities of this, 

 going back only to the grandparents, may be taken from 

 human characteristics. One of the grandparents, in conse- 

 quence of his particular gene combination, may have been 

 dull and slow, but industrious and ambitious. Another 

 grandparent may have had natural quickness and intelli- 

 gence, but also laziness and lack of ambition. Some of the 

 grandchildren may get from one of these grandparents the 

 genes that yield industry and ambition, from the other the 

 genes that yield quickness and high intelligence. In this way 

 superior individuals are formed, men that make a success of 

 life. Other grandchildren will get the genes that yield slow- 

 ness, dullness, laziness and lack of ambition all combined. 

 These are the ne'er-do-wells, the failures. And great num- 

 bers of other recombinations may be made from the genes 

 of the four grandparents. 



The various methods of combining genes are what give 

 origin, in any stock, whether of plant, animals or man, to 

 exceptional individuals, both superior and inferior. From 

 the same set of genes may be produced, by combining them 

 in various different ways, superior individuals, mediocre 



