CHAPTER IX 



BLENDING INHERITANCE 



1. Relative Value of Dominance and Segre- 

 gation 



Of the three fundamental principles which underlie 

 "Mendel's law," namely, segregation, independence of 

 unit characters, and dominance, the principle of 

 dominance has been found to hold true in a surpris- 

 ing number of cases and in relation to very diverse 

 organisms, notwithstanding the fact that the time 

 spent in the investigation of dominance, as that term 

 is now understood, has been comparatively short. 

 Doubtless future experimentation will demonstrate 

 the existence of dominance to a far greater extent 

 than has at present been discovered. 



Its universal application is by no means assured, 

 however, since the mathematical precision with which 

 it works, that following its discovery in 1900 has so 

 captivated the biological world, is beginning to give 

 way in the face of many exceptions which have been 

 steadily accumulating. 



Even Mendel himself noted certain exceptions to 

 the law of dominance, and his followers have pointed 

 out with increasing emphasis that it is subject to 

 many modifications. It is now understood, indeed, 



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