116 



THEORY OF EVOLUTION 



One of these mutants, called "eyeless" (fig. 56, 

 (a, a 1 ), is variable the eyes are often entirely 

 absent or represented by one or more groups of 

 ommatidia. The outline of the original eye, 



FIG. 56. Group IV. (See text.) 



so to speak, is strongly marked out and its 

 area might be called a rudimentary organ, if 

 such a statement has any meaning here. 



The other figure (b) represents "bent", so 

 called from the shape of the wings. This mu- 



