Modification of Germinal Constitution of Organisms 225 



katalyzer, or, in some cases, perhaps, to the stereoisomeric 

 relations in the molecules which are attached to the fatty 

 base. The well-known changes which are possible in the 

 case of lipochrome colors, changing with sharp alternative- 

 ness from red to yellow, from orange to white, or vice 

 \-ersa, are quite possibly due to reversibility in some enzyme 

 ^\'ithin the germ cell, and this reversed action remains 

 reversed until such time as it is again changed in its direction 

 bv incident factors. That this is apparently the correct 

 explanation of the behavior of this particular type of 

 pigmentation activity seems to be fully shown by many 

 experiments. 



In many of my experiments germ cells that were pro- 

 duced at a time when the lipochrome pigment in the parents 

 was yellow, produced yellow progeny, but when the color 

 had been experimentally reversed they gave white, orange, 

 or red progeny, depending upon the direction of change in 

 the parent. These results strongly indicate that the inter- 

 pretation which I have placed upon this type of germinal 

 variation is the correct one. 



Variations in these lipoid color characters are common in 

 plants and animals, and characters based upon these are 

 widely used as specific dilTerentials, and they are permanent 

 so long as a given state of equilibrium exists. This state 

 of equilibrium, however, can be reversed or upset, producing 

 reversed conditions, and these reversed conditions can again, 

 after an indefinite period, be brought back to the first 

 condition, or some other condition, by incident forces. It is 

 almost heresy at the present time to suggest the possibihty 

 of reversibility in evolutionary action, but the reversible 

 nature of many characters of importance in evolution is b}- 

 no means unthinkable and is susceptible of experimental 



