104 THEORY OF EVOLUTION 



Some of the characters of the mutant types 



are shown in figures 53, 54, 55, 56. The draw- 

 ing of a single fly is often used here to illustrate 



more than one character. This is done to econ- 

 omize space, but of course there would be no 

 difficulty in actually bringing together in the 

 same individual any two or more characters be- 

 longing to the same group (or to different 

 groups). Without colored figures it is not 

 possible to show many of the most striking dif- 

 ferences of these mutant races; at most dark 

 and light coloring can be indicated by the 

 shading of the body, wings, or eyes. 



Group I 



In the six flies drawn in figure 53 there are 

 shown five different wing characters. The 

 first of these types (a) is called cut, because the 

 ends of the wings look as though they had been 

 cut to a point. The antennae are displaced 

 downward and appressed and their bristle-like 

 aristae are crumpled. 



The second figure (b) represents a fly with a 

 notch in the ends of the wings. This charac- 

 ter is dominant, but the same factor that pro- 



