Correlation and Variation in the Toad 577 



taken of thirteen characters, including both external dimensions 

 and internal organs. The numerical ratio between the sexes was 

 found to be 658 males to 1000 females. The sexes are perfectly 

 distinct with respect to size, variability and correlation. The 

 females are on the whole about 24 per cent larger, 23 per cent more 

 variable and 10 per cent better correlated than the males. The 

 internal characters are about four times as variable as the external. 

 The ratios between the average values of pairs of characters 

 remain the same in the two sexes. The distributions are all skew 

 and nearly all negatively, apparently the result of including individ- 

 uals of all ages over one year. 



The correlation coefficients are all relatively high. The exter- 

 nal characters although less variable than the internal, are in the 

 males 51 per cent and in the females 30 per cent better correlated 

 than the internal characters. Those individuals above the aver- 

 age in any pair of characters show much less "scatter" about the 

 regression line than those below the average. 



In the general discussion these results are compared with those 

 of other observers. Some of the points mentioned are the relation 

 between efficiency and mass or dimensions in external and internal 

 characters; the extremely high variability of internal characters; 

 the relation between variability and correlation. 



The conclusion is reached that from the side of fitness or sur- 

 vival conditions of correlation here seem to be more fundamental 

 than conditions of variability, and that the general subject of cor- 

 relation is of increasing importance. 



Ill THE DATA 

 I Material 



The subjects from which these data^ were secured consisted 

 of a society of 441 individuals of the Common American Toad 

 (Bufo lentiginosus americanus, Le. C.) The society was one 

 found on Cedar Point, Ohio, a low sandy point 200 to 300 yards 

 wide extending for six or seven miles obliquely into Lake Erie and 



1 The data were secured during the summer of 1905 at the Lake Laboratory of the Ohio State 

 University. 



