K^—r-. -, ,1 



gen«iationt 



Fig. 141. Results of selection for a reduced number of bristles continued for 64 generations among 

 the inbred descendants of a single pair of flies. The heavy line shows the percentage of flies with- 

 out bristles in each generation. Note that little change occurs after the 17th inbred generation. 

 (After Payne.) 



I 1»' 12 M I* 



8f ne ra 1 1 Da« 



■nc- 



FiG. 142. Results of selection for an increased number of bristles made throughout 60 inbred g*-- 

 rations upon the same initial stock as is mentioned in the description of Fig. 141. The hea\->' line 

 shows the percentage of four-bristled (normal) flies in each generation. Note the progressiw 

 increase which continued as late as generation 55. (After Payne.) 



