576 Wm. E. Kellicott 



among a large number of characters — in fact, throughout the entire 

 organization. This condition of balance is to a certain extent 

 measurable by coefficients of correlation which are merely indices 

 of the corresponding change in a given character accompanying a 

 certain change in another given character — "relative" and "sub- 

 ject." The ideal method of approaching this matter is of course 

 through multiple correlations involving the relation of at least three 

 characters but this method is not practicable because of the time 

 involved in carrying through such calculations. Consequently the 

 method adopted here is merely to calculate the coefficients of cor- 

 relation between all of the measured characters in pairs. 



The material from which the data were drawn was unusually 

 favorable for such a study. Toads were readily secured, were not 

 affected by capture and were easily kept in nearly normal condi- 

 tions during the brief time elapsing between their capture and 

 measurement. The group studied was a perfectly homogeneous 

 one, all in excellent nutritional condition, with precisely similar 

 environmental conditions, and quite isolated geographically. 

 The number measured and weighed was not large absolutely 

 (425) but the fact that practically an entire colony of the particular 

 variety under observation was collected and measured is almost 

 unique. The results are therefore at least free from errors due to 

 the sampling of a larger population, errors which easily may be so 

 great as to vitiate results even though a most careful preliminary 

 study of the organism and its habits may have been made and 

 particular care taken to procure a "random" sample. 



The fact that the subjects w^re of various ages, the growth phe- 

 nomena not being taken into account, renders the data given here 

 of no value for certain special purposes, but for the relations which 

 are being sought here this is not an objection. We are dealing 

 here with the conditions of correlation and variation in a total 

 natural society of normal individuals. 



II SUMMARY 



The material under consideration consisted of practically an 

 entire colony of the common toad. Accurate measurements were 



