THE AMERICAN NATURALIST [Vol. LIV 



the latter on the basis of these agglutination tests. In 

 the case of the tissues we have to assume the existence of 

 individuality-differentials which are composed of mul- 

 tiple chemical groups; therefore Mendelian heredity- 

 would be that of multiple factors. It is not improbable 

 that even in the case of tissues the number of these 

 groups is limited and that all the individuals of the same 

 species have a choice only between a relatively small 

 number of groups which is characteristic of each species 

 and that the different individuals of a species differ from 

 each other through the combination of these groups which 

 each individual possesses. Other chemical groups would 

 be characteristic of species and in this case also the num- 

 ber of groups which constitute a species differential may 

 be limited. 



The explanation for the facts of inheritance of the indi- 

 viduality-differentials which we attempted in this note 

 is regarded by us at present as of an entirely provisional 

 character. So far, however, it seems to agree with the 

 facts as they are known ; but we have no doubt that as 

 investigations progress still further it may require cer- 

 tain, perhaps t'argoing, modifications. Tt finds, however, 

 support in the investigations of Landsteiner, 6 Pick and 

 Obermeyer and others who have shown that the immune 

 reaction-specificity of protein substances can be experi- 

 mentally altered through changes in chemical side chains 

 which are added to these proteins. 



«Karl Landsteiner u. Hans Lampl, Biochem. Zeitsch., 1918, LXXXVT, 342. 



