248 Mechanism of Mendelian Heredity 



egg or sperm), the pure purpuratus should have twice 

 the enzyme mass of the hybrid. It is known that the 

 velocity of a chemical reaction increases in proportion 

 with the mass (or in some cases in proportion with 

 the square root of the mass) of the enzyme; the cross- 

 bars should therefore develop faster in the pure than 

 in the hybrid breeds, as was observed by Moore. It 

 was, however, not possible to obtain quantitative data. 



On the other hand, it is obvious that this reasoning 

 would not hold for all cases. Thus when beans with 

 violet flowers are crossed with white-flowered beans 

 the hybrids are pale blue, which indicates that the 

 hybrids have less pigment than the pure violet. Now 

 we know that the mass of enzyme does not influence 

 the chemical equilibrium but only the velocity of the 

 reaction. The hybrids and pure violets differ, how- 

 ever, in the mass of violet pigment formed, that is to 

 say, in regard to the equilibrium. Hence the idea that 

 the determiners are enzymes or give rise to enzymes is 

 probably not applicable to cases of this type. 



The experiments on the heredity of pigments are 

 at present almost the only ones which can be used for 

 an analysis of the chemical nature of the character 

 and its possible determiner. The important work of 

 G. Bertrand' and of Chodat^ on the production of 



'Bertrand, G., Ann. d. VInst. Pasteur, 1908, xxli., 381; Bull. Soc, 

 Chim., 1896, XV., 791. 



' Chodat, R., Arch. d. Sc. phys. et nat., 1915, xxxix., 327. 



