A RECESSIVE CHARACTER AND SELECTION 161 



The object of the experiment was to select toward the normal 

 long wing. In some instances individuals with shorter wings 

 were given preference in selection, for the reason that they ap- 

 proached more nearly the long-wing type in form and venation. 



It is assumed that the expression of this somatic character, 

 vestigial wing, is an index of the germinal constitution. In any 

 selection experiment, without the progeny test, selection is 

 effective only when the somatic character is an index of the 

 germinal constitution to some degree at least. However, en- 

 vironmental factors may affect the somatic expression and thus 

 render selection less effective. 



III. EXPERIMENTAL DATA 



1 . Selected series A 



This series began, as described in section II, with a mating of 

 a vestigial-winged male and female taken at random, and was 

 contmued for thirty-four generations. Table 1 gives the means, 

 standard de^dations, and coefficients of variabihty of males and 

 females in each generation. The males and females are treated 

 separately in order to show any sex differences. 



a. Effect of selection. In table 5 are found the weighted aver- 

 age wing lengths of parents and offspring for each generation in 

 selected series A. By an inspection of text figure 1, which is 

 constructed from table 5, it is at once seen that no increase in 

 size of wing was made during the process of selection. This is 

 further borne out by the correlation between the average wing 

 length of the parents and that of the offspring which is 



r = + 0.329 ± 0.103. 



This correlation is not significant when judged by the probable 

 error. To be sure, a marked correlation is not necessarily a 

 measure of the amount of progress made by selection, for en- 

 vironment may produce a significant correlation, but it is ob- 

 vious that if there is no significant correlation between the size 

 of the parents and the size of the offspring selection is of no 

 avail. 



