THE RELATION OF VARIABILITY TO FOOD 



SUPPLY AS ILLUSTRATED BY THE WHITE 



DAISY, CHRYSANTHEMUM LEUCANTH- 



EMUM L. AND THE YELLOW PERCH, 



PEKCA FLAVESCENS MITCH.^' 



Notwithstanding the numerous biological problems 

 which have been attacked by means of statistical methods 

 during the last ten years, an absence of evidence concern- 

 ing the effect of food supply upon the variability of 

 organisms exists. It was with a view toward obtaining 

 data bearing upon this particular problem that the present 

 investigation was undertaken. While the natural environ- 

 ment by no means furnishes conditions for obtaining the 

 best results, it seemed advisable, at least in a preliminary 

 survey of the subject, to adopt such a method. 



In the first part of the investigation results were ob- 

 tained from the ray flowers in two groups of the common 

 white daisy {Chrysanthemum leucanthefnum L.), 500 

 heads growing on rich soil (group A) and 500 heads 

 growing on poor soil (group B) were examined. The 

 specimens were collected on the same day and from 

 localities approximately one mile apart. While the mode 

 (33) and the mean (28.786) were much greater in 

 specimens growing on rich soil (cf. Ludwig, Tower, Shull, 

 etc.) than in those on poor soil (21) (25.632), the index 

 of variability in each group was approximately the same 

 taking into consideration the probable error. 



In the second part of the investigation results were ob- 

 tained from the number of pore-bearing scales in the 

 lateral line of two groups of yellow perch (Perca fla- 

 vescens Mitch.) obtained in Lake Erie. The one group 

 (group A) was procured from a locality (cove in San- 

 dusky Bay) where there was every reason to believe that 



♦Reprinted from Science, N. S., vol. 25 (1907), p. 728. 



