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the variation in breadth and length it is to be noted that the 

 variation in breadth is twice as large as that in length, which 

 indicates that we do not err on the side of obtaining too low a 

 coefficient of variation in size of the wing when we accept the 

 C. V. for the breadth as a criterion of the C. V. for size, an 

 assumption forced on us in the case of the drones because of 

 the torn wing tips making the length determinations impossible. 

 The frequency polygon showing the variation in length of 

 the vein part b—d, is as follows : 



Fig. i8. Frequency polygon of the variation in measurement i-</ (see fig. 

 ii) in right fore wings of 279 honey bee workers taken from laboratoi-y hive at 

 one time; mean length of this wing part, 21.7 micrometer units; index of 

 variability, 1.223; coefficient of variation, 5.63. 



The mean length is 21.7, the mode 22, the standard devia- 

 tion 1.22, and the coefficient of variation 5.63. Here, as in the 

 drones, the variation of the part of a vein definitely subtended 

 by the forking of the vein or origin of a branch, is more than 

 twice as large as the variation in size of the wing as indicated 

 by the variation in breadth. 



