70 Can Science Explain Life? 



species. Such minor changes take place with 

 equal facility in either direction, from which it 

 appears that the corresponding variations in the 

 spirazine pattern must be completely reversible 

 and must be confined to local changes only, such 

 as the coupling or uncoupling of the adjacent 

 spirazines through their carbonyl and amino 

 groups, so as to produce that peculiar allelo- 

 morphism which is characteristic of Mendelian 

 heredity but without producing any permanent 

 change in the spirazine pattern as a whole. 



Any feature which is transmitted by Mendelian 

 heredity will appear either completely or not at 

 all. It will make its appearance to exactly the 

 same extent regardless of whether only one or 

 both of the germ cells contain the positive or 

 dominant characteristic. This can be explained 

 only on the theory that the physiologically active 

 agents in such cases are not the dominant spira- 

 zine complexes themselves but certain hormone- 

 like substances in the dispersed or molecular state 

 which were liberated therefrom. If either one or 

 both of the germ cells contain the dominant char- 

 acteristic, then the above-mentioned substances 

 will be present in the protoplasm and will produce 

 their specific effects. 



