216 



T. H. MORGAN AND SABRA COLBY TICK. 



BACK-CROSS EN MASSE. 



This same mating was again made both in mass and in pairs. 

 The expectation is equality of long and rudimentary wings. 

 The mass cultures gave: 



Long 9 .... .341 



Long d" .337 



Rudimentary 9 Si 



Rudimentary c? 64 



When the experiment was made with pairs the following totals 

 were obtained, (with a ratio of I. : .63): 



Long 9 1,676 



Long d" I-43I 



Rudimentary 9 93O 



Rudimentary d 1 1,022 



For detailed comparison the counts of the two mass cultures 

 and of the 29 pairs taken separately are given in Table II. 



TABLE II. 



BACK-CROSS PAIRS. 



