NO. 533] NUCLEUS AXD CYTOPLASM IX HEREDITY 301 



at any one of six places. These substitution groups can 

 be shifted or replaced indefinitely without disrupting the 

 ring itself. Still different effects are obtainable by the 

 union of one or more rings (generally still retaining some 

 of the substitution groups) directly with one another, or 

 through the intermediacy of a third element or radical. 

 In the numerous coal-tar colors, the color, which is one 

 of the most obvious "characters." does not lie as such 

 in the benzene ring itself, but is determined by the rad- 

 icals attached to the ring, and in certain groups perhaps, 

 in part by the manner in which two or more rings are 

 united. If, for instance, into a molecule of azobenzene a 

 radical of the amido-group (NH 2 ) is introduced, a body 

 is constructed which through salt formation yields a 

 dye. If instead of the amido-group a hydroxyl group 

 is introduced, the result is likewise a dye but one of dif- 

 ferent color. And so a large series of tints may be pro- 

 duced by varying the substitution groups which replace 

 H in the principal molecule. 



We have constantly increasing evidence, finding re- 



fundaniental stereometrical condition of the egg-plasm. 

 And V. R. Lillic'-' has suggested the possibility that a 

 specific polarity and symmetry arc characteristic of the 

 ground substance common to all cells of the organism. 

 Stereochemistry is based on the assumption that the 

 combining forces of an atom act in certain definite direc- 

 tions in space. This same conception of orientation must 

 be carried on to the more complex organic units, the 

 stereometrical relations of which, in turn, are but the 

 continued expression, under other conditions, of the 

 original atomic combining forces. And this being true, 

 it seems reasonable to look upon the whole organism as 

 •nit the further expression of such elemental factors. 



In view of the facts regarding the closeness of identity 

 ot corresponding proteins of nearly related species, we 

 must conclude that between two individuals of the same 



