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- 



