LINKAGE GROUPS 93 



called miniature. The light color of the drawing may 

 be taken to represent yellow body color. 



In the last figure (/) of "club," the wings are 

 pads, essentially in the same condition that they 

 are in when the fly emerges from the pupa case. 

 Not all the flies of this stock have the wings in this 

 condition ; some have fully expanded wings that ap- 

 23ear normal in all respects. Nevertheless, about the 

 same percentage of offspring show the pads irrespec- 

 tive of whether the parents had pads or expanded 

 wings. The flies of this stock show, however, another 

 character, which is a product of the same factor, and 

 which is constant, i.e., repeated in all individuals. 

 The two bristles on the sides of the thorax are con- 

 stantly absent in this race. 



There are many different eye colors in Group I, 

 ranging from a pure white eye to vermilion, which 

 could be shown onlv bv the use of colored drawings. 



GROUP II 



The hereditary elements of members of Group 

 II are carried by one pair of the two large bent 

 chromosomes. 



In the first drawing (a) of figure 41 which contains 

 members of Group II, the wings are almost entirely 

 absent or "vestigial." This condition arose at a single 

 step and breeds true, although it appears to be influ- 

 enced to some extent by temperature, also by modi- 

 fiers that sometimes appear in the stock. 



