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SCIENCE 



[N. S. Vol. XXV. No. 645 



of vessels, which are continuous with the 

 hearts but bend outward and upward and 

 pass through the dorsal musculature into 

 the somite in front, to sets of skin capil- 

 laries there on the dorsal rami of the para- 

 podia and on the dorsal surface of the 

 somite. Blood passes through these sets of 

 capillaries, with the blood from the neph- 

 ridial capillaries, into a pair of vessels 

 ■which empty blood into the dorsal vessel 

 immediately after the peristaltic, wave of 

 contraction in the dorsal vessel has passed 

 the point of connection. 



The Relation of Variability to Food Supply 

 as illustrated hy the white daisy, Chry- 

 santhemum leucanthemum L. and the 

 yellow perch, Perca flavescens Mitch.: 

 L. B. Walton, Kenyon College. 

 Notwithstanding the numerous biological 

 problems which have been attacked by 

 means of statistical methods during the 

 last ten years, an absence of evidence con- 

 cerning 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 pres- 

 ent investigation was undertaken. While 

 the natural environment by no means fur- 

 nishes 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 re- 

 sults were obtained from the ray flowers in 

 two groups of the common white daisy 

 {Chrysanthemum leucanthemum L.), 500 

 heads growing on rich soil (gi'oup A) and 

 500 heads growing on poor soil (group B) 

 were examined. The specimens were col- 

 lected on the same day and from locali- 

 ties 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 ap- 

 proximately the same taking into con- 

 sideration the probable error. 



In the second part of the investigation 

 results were obtained from the number of 

 pore-bearing scales in the lateral line of 

 two groups of yellow perch (Perca flaves- 

 cens Mitch.) obtained in Lake Erie. The 

 one group (group A) was procured from 

 a locality (cove in Sandusky Bay) where 

 there was every reason to believe that the 

 food supply approached the maximum, 

 while the other (group B) was collected 

 from the rocky shores of an island some 

 ten miles distant where the food supply 

 apparently approached the minimum. 

 Again the index of variability showed no 

 decided difference when the probable error 

 was considered. 



In connection with the ray flowers of the 

 daisy it is of interest to note that specimens 

 from rich soil exhibited a tendency toward 

 an even number of ray flowers, while those 

 from the poor soil had a tendency toward 

 an odd number of ray flowers. This how- 

 ever may be a coincidence, although taken 

 into consideration with the differences, a 

 somewhat remarkable one. No decided 

 tendency toward the Fibonacci series was 

 apparent. 



The computations were made by the 

 ordinary method, checked by logarithms 

 and a Burrough's adding machine. There 

 are a number of possible errors minimizing 

 the value of the results. These, together 

 with the literature bearing upon the sub- 

 ject will be considered in the final paper. 



While the above results suggest that food 

 supply does not materially affect variabil- 

 ity, it is evident that work upon a larger 

 number of specimens, as well as carefully 

 controlled experimental investigations, 

 where the effects of different groups of 

 stimuli may be segregated, will be neces- 

 sary before any final conclusions may be 

 drawn. 



