CHAPTER I 



THE MUTUAL INDEPENDENCE OF HEREDITARY 

 CHARACTERS 



/. The Combination of Specific Characters Out of 

 Hereditary Characters 



Among the many advantages which have lent such 

 a prominent significance to the theory of descent in the 

 investigation of living nature, the shattering of the old 

 conception of species occupies an important place. For- 

 merly every species was regarded as a unit and the total- 

 ity of its specific attributes as an indivisible concept. Even 

 the latest theories on heredity accept this concept as one 

 that does not require any further analysis. 



But if the specific characters are regarded in the light 

 of the theory of descent it soon becomes evident that they 

 are composed of single factors more or less independent < 

 of each other. One finds almost every one of these fac- 

 tors in numerous species, and their varying groupings^- 

 and combinations with less common factors causes the 

 extraordinary diversity in the organic world. 



Even the most cursory comparison of the various or- 

 ganisms leads, in this light, to the conviction of the 

 composite nature of specific characters. The power to 

 produce chlorophyll and, by means of this, in light, to 

 decompose carbon dioxide, is evidently to be regarded as 

 a property which, in great measure lends to the botanical 

 world its peculiar stamp. This power, however, is lack- 

 ing in many groups throughout the system, and therefore 



