Vol. XXXIV. February, 1918. No. 2. 



BIOLOGICAL BULLETIN 



HEREDITY FROM THE PHYSICO-CHEMICAL POINT 



OF VIEW. 1 



RALPH S. LILLIE. 



Heredity, the power of reproducing its like, is a property of 

 all forms of living matter from the lowest to the highest. Broadly 

 speaking, whenever a universal property or mode of action is 

 found, the presumption is that its basis is fundamentally simple, 

 for repetition is characteristic of simple rather than of complex 

 conditions and objects in nature: in general, the fewer the var- 

 iables the more constant the phenomenon. We have therefore 

 to seek for some general or fundamental structural or physico- 

 chemical peculiarity of living things which enables their sub- 

 stance to build up substance of a similar kind. Any form of 

 protoplasm acts as a center of construction of similar forms. 

 At present we are not concerned with the further fact that this 

 reduplication is ' not perfect, that varieties appear and that 

 diversity has arisen in the course of evolution. This process of 

 divergence is gradual, and even in mutants the differences from 

 their parents are slight compared with the resemblances; the 

 essential fact is that the type is preserved, and that normally 

 the organism appears unable to construct living matter of other 

 than its own kind. The main question is why any species of 

 organism tends so strongly to retain its specific character. 



Apparently the most universal property of living matter is its 

 power of proliferation. Out of materials and energy taken from 

 the surroundings it constructs more living matter of the same 

 kind. In other words, the power of growth is innate; and if the 

 available nutritive and other materials are sufficient the quantity 

 of the specifically organized and active living substance tends 

 continually to increase. The degree of increase possible under 



1 From the Laboratory of General Physiology, Clark University. 



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