506 PROTOPLASM 



duction are now no longer problems in biology or medicine but 

 problems in physics and chemistry. 



Speculations on the physical and chemical nature of the heredi- I- 

 tary substance or particle (the gene) are based on the main thesis it' 

 of this chapter, viz., that protein is the primary vital substance. % 

 Such a conclusion in regard to heredity is reached by Demarec. t 

 He views the gene as a protein complex or possibly a single i 

 protein molecule. f. 



Estimations by Muller of the size of the gene (highly specula- \ 

 tive in themselves, for we are not yet certain that the gene is a 

 definite individual particle) place it at 50 m^t. This is ten to 

 twenty times the size of large protein molecules. Gowen and 

 Gay place the maximum gene volume at 1 X 10~^^ cm^. 



