A RECESSIVE CHARACTER AND SELECTION 169 



From tables 3 and 7 it is to be seen that the coefficients of 

 variabiUty have decreased in the generations produced under high 

 temperature, but that the standard deviations are about the same. 

 This does not necessarily mean that the range of variation has 

 decreased. Since the coefficient of variability is obtained by 



dividing the standard deviation by the mean, C = t7, it is quite 



obvious that as M increases, C decreases if <r remains constant. 

 When dealing with biological materials of the same kind, stand- 

 ard deviation is sometimes a much safer criterion of variability 

 than the coefficient of variability. 



Another fact brought out by an inspection of table 7 is that 

 there is little difference between the males and females with 

 regard to length of wing. The average for the males is 45.90 ± 

 0.26 and for the females 42.50 ± 0.35 (F29 to F35). By leaving 

 out of the calculations the F29 generation which underwent some 

 of its development outside of the incubator, the averages become 

 49.25 ± 0.23 for the males and 48.35 ± 0.27 for the females. 

 This shows a much smaller difference than above, and is not 

 significant when judged by their probable errors. Judging from 

 the very large differences existing between the males and females 

 in the series outside the incubator, it seems that the males are 

 more easily affected by high temperature than are the females, 

 but that under constantly high temperature both males and 

 females were equally affected. 



3. Form of wings 



Some of the types of wings found in these series are shown in 

 plate 1. There is great variability in the size, shape, and vena- 

 tion. A very good graded series could have been obtained from 

 the normal vestigial type (1) to the normal long wing (14) . Figure 

 13 shows a conunon type of wing produced in the high-tem- 

 perature series and less frequently in the other series. It is in 

 size and venation like a normal long wing. Other types similar 

 to 'strap,' truncate, and beaded as described by Morgan ('16) 

 appeared. 



