A RECESSIVE CHARACTER AND SELECTION 173 



incubator, having a wing of the general form shown in plate 1 , 

 figure 13, was mated to small vestigial-winged females from the 

 original stock. This cross was carried through the second gen- 

 eration and was kept from the beginning in the incubator. 

 Table 8 summarizes the means, standard deviations, and co- 

 efficients of variability of the males and females separately. It 

 is to be noted that the variability in the second generation, when 

 judged by the standard deviation, is greater than in the first — 

 a condition to be expected if differential factors were involved. 

 The difference between the males in the first and second genera- 

 tions is not highly significant when judged by the probable errors, 

 but that between the females is. However, the variability of the 

 males is greater in the second generation than in the first. The 

 average variability of the males and females combined in the Fi 

 generation is 5.81 ± 0.48 and in the F2 9.93 ± 0.76. That the 

 males are more affected than the females is again brought out 

 in this cross. 



The correlation between the averages of wing lengths in the 

 parents and in the offpring for the 'crossed-in' series is expressed 

 by 



r = 0.528 ± 0.086 



This probably indicates that both parents and offspring were 

 produced at a time favorable to the development of large vestigial 

 wings. 



If the increased size and variable form of wing are due to 

 factors, the original stock must have contained at least some of 

 these factors since, under high temperature, the size and form of 

 wing were much affected in the simple selected series (table 1). 

 Morgan ('16) writes concerning the vestigial wing character: 

 ''This condition arose at a single step and breeds true, although 

 it appears to be influenced to some extent by temperature, also 

 by modifiers that sometimes appear in the stock." 



Morgan and Lynch ('12) state that the vestigial wing was 

 crossed to the long wing and segregated again in order to in- 

 crease viability. Hence, factors may have been introduced and 

 carried in the stock from that time, and were effective only 

 when temperature was favorable. 



THE JOURNAL OF EXPERIMENTAL ZOOLOQY, VOL. 27, NO. 2 



