168 



ruYsiouHihM. <;h.\/rncs 



addition <>f the genes -cute echinus, crossveinless, cut, vermilion 

 garnet, and also the calculated values of b and A- 



Table 20 



From llcrsiii 



This table shows that some mutant genes increase, others 

 decrease, the Bar action and are, in Bridges' terminology, plus 

 or minus modifiers. If more than one are involved, the action 

 might be cumulative or only of the same type as with one of the 

 members. The same gene may even act in one combination as 

 a plus and in another as a minus modifier. The values of b and k 

 are influenced in a similar way. There is no relation between the 

 normal, known actions of these genes and their actions in these 

 combinations. But the facts as a whole seem to me to indicate 

 that the reactions controlled by these mutant genes are primarily 

 of a quantitative type, shifting the velocities of some processes in 

 one or another direction, and that the time relations of these and 



