THEORY OF EVOLUTION 71 



fects as well. The females are almost com- 

 pletely sterile, wliile the males are fertile. The 

 viability of the stock is poor. When flies Avith 

 rudimentary wings are put into competition 





Fic. 34-. Mutant race (if t'riiit fly, called rudiinentarv. 



with wild flies relativelj^ few of the rudimentarj'^ 

 flies come through, especially if the culture is 

 croAvded. The hind legs are also shortened. 

 All of these effects are the results of a single 

 factor-difference. 



One may A^enture the guess that some of the 

 specific and A^arietal differences that are char- 



