BRISTLE INHERITANCE IN DR080PHILA 



II. SELECTION 



EDWIN CARLETON MACDOWELL 



Slalion for Experimental Evobition, Cold Spring Harbor, Long Island 



TEN FIGURES 



CONTENTS 



Previous results ] 09 



High selected race Ill 



Frequency distributions by generations HI 



Means 112 



Extremes of variations 116 



Standard deviations 117 



Discussion of the distributions 119 



Comparison of parents and offspring 119 



Conclusions 123 



Low selected race 124 



Return selected race 125 



Means .' 125 



Standard deviations 1;G 



Conclusions i;?2 



Extracted low selected race 134 



Means 135 



Standard deviations 137 



Conclusions 137 



Discussion 139 



The role of environment 139 



Accessory factors vs. a variai)le factor 142 



Summary 145 



PREVIOUS RESULTS 



The general scheme of the inheritance of the extra bristles 

 that appeared on the thorax in a race of Drosophila ampelophila 

 has been demonstrated in a previous account.' It was shown 

 that the extra-liristled condition behaves as a Mendelian reces- 



' MacDowell: Bristle inheritance in Drosophila. I. Extra l)risfl('s. Jour. K\]). 

 Zool., vol. 19, no. 1, 1915. 



109 



THK, .lor;i!NAL r)F EXPERIMENTAL ZOOLOGY, VOL 23, NO. 1 



