1920] COULTER— HEREDITY 46 



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product # 3 , insulated by its antibody, will pass on at cell division 

 to the daughter protoplast. Early in the life of the daughter 

 there must exist an A equilibrium. The inevitable program will 

 then be followed, until finally the X equilibrium is reached. A 

 very critical assumption is made at this point. The insulation of 

 # 3 by its antibody is a phenomenon of colloidal chemistry. Similar 

 colloidal reactions are known to be reversible. The formation of 

 the antibody for x 3 took place at the inception of the Y equilibrium, 

 which was characterized by the effective insulation of x*. The X 



equilibrium, however, which now recurs during the following 

 generation, is conducive to the free and active existence of any 

 by-product of the x type. When the X equilibrium is reached in 

 the life of the daughter protoplast, therefore, a dissolution of the 

 antibody will occur and x 3 will be released. 



With the X equilibrium now in existence, it is certain that 

 reactions of the x type will take place. Which one of the possible 

 x reactions occurred was in the first generation a matter of chance. 

 In the present instance, however, the presence of by-product x 3 

 will exert a determining influence. The result, eliminating external 

 stimuli of an unusual intensity, will be that the x 3 reaction and the 

 x 3 by-product again stimulate the protoplast in a characteristic 

 manner, developing in the daughter the same characteristic that 

 was present at a similar stage in the life of the mother. 



This theory accounts for the origin of the hereditary mechan- 

 ism in terms of by-products and antibodies which insulate them. 

 These various antibodies must form an important constituent of 

 "modern" chromosomes, but there must also be present some 

 more stable and homogeneous framework. 



The release of the determiners (by-products) at the appropriate 

 moment is referred to phenomena of colloidal chemistry. It is an 

 open question whether this release is reflected by visible changes 

 in the chromosomes. If so, a given locus on a chromosome should 

 be seen in a loose or "open" condition only during a brief phase 

 of the life history. Xo doubt this point would be hopeless to 

 ascertain in any very accurate way. 



As for the determiners themselves, these are visualized as 

 by-products of metabolism, chemically active substances. The 



