438 p. W. WHITING 



Neither the forms of the curves nor the displacements of the 

 points are to be taken as in any way exact. They are merely 

 approximations which express the genetic and apparent physi- 

 ological relationships involved. 



Curve and point T show amount of inhibitor in the type moth. 

 The colors of the regions of the wing are printed below in the 

 line marked T. Dots, curves, and colors of regions are corre- 

 spondingly labeled for the other color varieties. The regions 

 of the wings are not, of course, marked off definitely as expressed 

 by the perpendicular lines, but grade into each other more or 

 less as shown by the curves. 



The recessive variation, black, (b), is represented as a general 

 lowering of the inhibitor. Its point is placed four squares di- 

 rectly below that for type and its curve is correspondingly an 

 equal distance below the type curve. Black, therefore, inhibits 

 pigment formation only in the white lines. Variation in this 

 respect obtains among individuals of black cultures. The moth 

 represented in figure o has only a trace of the white lines. 



The variation, dark mid-area, (d), darkens mid-area and 

 lightens base. Its point is placed one square below and to the 

 right of type. Its curve then is somewhat below that for the 

 color producer in the mid-area and slightly above it towards the 

 base. Dark, black has its point and curve four points below 

 dark. It may be seen to bear the same relation to black that 

 dark does to type. A comparison of the curves of black and 

 dark black shows how the 'ghost pattern' of dark seen in dark 

 black is formed. The greater distance from the color producer 

 curve of the curve for dark black at mid-area and the lesser dis- 

 tance towards the base accounts for the greater intensity of the 

 mid-area. • 



There is, as stated, much intergradation with type in the dark 

 mid-area moths. The points and curves shown in the diagram 

 represent only one grade. 



Sooty base has an action somewhat reverse to dark mid-area. 

 Heterozygous sooty (Si) has its point two squares above and 

 three squares to the left of type and homozygous sooty (S2) has 

 its point twice that distance from type. This brings the curves 



