GENETICS 147 



argument's sake, puts the case in the extreme, as he also does 

 the obverse case : 



But such as are most unlike are most disposed to friendship, just 

 as the dry desires the moist, the cold heat, and so on. . . . 



The contrary is most friendly to its contrary. 



It is clear that what he is in reality driving at is the 

 demonstration of the need of a genuine pair of symbiotic 

 opposites not by any means necessarily widely antagonistic 

 to establish evolution by joint operations (symbiogenesis). 



He tells us that that which desires, desires what it stands 

 in need of (i.e., reciprocity), and that which stands in need 

 (what is there that does not?) is friendly to that of which it 

 stands in need. (Hence genuine symbiosis involves friendliness 

 and not hostility.) 



He was, of course, also well aware that "the more wicked 

 men are the more hostile they are to each other," so that the 

 degrees of antagonism would be quite different in accordance, 

 as we should say, with symbiotic possibilities. 



Like good and like bad are antagonistic to each other, but 

 in totally different degrees and to totally different purposes. 



The antagonism of the former is capable of finding, and 

 usually does find, relief in emulation and subsequent blending 

 of the results of work, while that of the latter produces the 

 intense competitive "struggle for existence." 



Allelomorphism, like friendship, thus ultimately depends 

 on mutual usefulness, and "friendly" antagonism frequently 

 may not mean much more than the sacrifice of the lower for 

 the higher. 



Mendelian segregation has brought to light the fact that 

 the presence of certain " characters " is not always indicated by 

 the ordinary appearance of the individuals; not always does 

 the plume proclaim the fowl. It is necessary, in order to gauge 

 its composition, to " break up," as it were, an organism by the 

 selective effects of crosses followed by in-breeding, which I call 

 genetic manipulation. I have already indicated that patho- 

 logical components gradually tend to give a peculiar 



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