GENERAL RELATIONS IN INHERITANCE 307 



produce offspring having nine different gene combinations. 

 One of these for example is the variety 



ABcDg 

 ABcDg 



This is brown, in consequence of the presence of cc; also 

 there is no pattern on the hairs, in consequence of the 

 presence of gg. Such solid brown animals are characterized 

 as chocolate in color; they constitute a new variety. 



In this way, by diverse crosses among the original five 

 color varieties, many diverse color varieties were formed. 

 Nachtsheim enumerates a considerable number of these, 

 showing the different gene combinations that they possess: 

 lilac, madagascar (mottled yellow), light lilac, orange, 

 sandy, and so on. By crossing among the original five color 

 types, a large number of additional color types have been 

 formed. 



New colors, new shapes and the like, appearing among 

 the descendants of a cross, are of course the result of inter- 

 action among the products of the genes brought together 

 in the new combinations. 



Thus, in sum, through the recombinations of genes in 

 biparental reproduction, great numbers of new types are 

 produced. Some of these show new combinations of char- 

 acteristics that before existed separately. Others show 

 characteristics increased in intensity, size, etc., etc., beyond 

 what previously existed. Still others show new character- 

 istics, not before manifested. By biparental reproduction 

 the variety among organisms is enormously increased. 



Lack of permanence of the types formed by recombina- 

 tion of genes. — So long as ordinary biparental reproduction 

 occurs in every generation, the characteristics produced in 

 the way just described are not permanent beyond the gener- 

 ation in which they are brought into existence. For in the 

 next generation a new combination of genes is formed. The 



