104 



H. E. EWING. 



while the former is not at all incrassate. Yet frequently the 

 incrassate nature of the cornicles has been used as a generic 

 character ! 



FIG. 15. Camera lucida drawings of same magnification showing extreme 

 fluctuations in size of two individuals of isolation No. n. The larger individual 

 is iisoi; the smaller 



Do these fluctuating variations group themselves about a 

 common mean as such variations normally do? Apparently 



FIG. 16. Camera lucida drawings, all of the same magnification, showing the 

 extremes of fluctuating variation in the shape of the cornicles of three individuals 

 (4273, 4271, and 42711) of the same fraternity. 



yes. In Fig. 17, I have plotted the frequency polygon for the 

 character of body length for the 477 individuals obtained in 



