THE GENESIS OF LIVING ORGANISMS 199 



individuals of the same race from one another. There are 

 racial characters, which distinguish the individuals of the same 

 species from one another. In the same way, there are specific, 

 generic and family characters. 



Mendel's inquiry was concerned only with racial charac- 

 ters : firstly, because these can be transferred in amphimixis 

 from one race to another, and secondly, because racial charac- 

 ters normally remain pure, and pass unaltered from parents 

 to offspring, which we know is not the case with the characters 

 peculiar to the individual. 



The questions lying at the basis of Mendel's investigation, 

 namely, whether the properties of organisms can be trans- 

 ferred as units from the parents to the children, could be 

 decided only by crossing races, for here there were characters 

 belonging quite certainly only to the father or to the mother. 

 In such a case it must appear whether the properties, in spite 

 of their close interweaving in the organism, are to be regarded 

 as units, or whether they mutually crowd one another out 

 and modify one another. Only here could it be proved beyond 

 all question whether the paternal characters mixed with 

 the maternal, or whether they suppressed one another, or 

 were interchangeable. 



Mendel finally decided the question in favour of the 

 characters being unchangeable magnitudes, which mutually 

 exclude one another. Even if he had discovered only this 

 one fact, he would have done science an immortal service, for, 

 by demonstrating the constancy of characters, he gave proof 

 of the constancy of the properties of all living organisms 

 whatsoever. Biology was shown the uniform building-stone, 

 which Nature uses unchanged for the production of so much 

 diversity, a diversity actually based not on variation but on 

 combination. Here at last we had in our grasp a biological 

 element which we could regard as an unalterable stone of 

 the mosaic, offering us firm foundation for all our researches. 



