Correlation and Variation in the Toad 595 



TABLE XIX 



Average degrees of correlation 



External characters with external characters only 837 912 



External characters with all characters 782 .851 



All characters with all characters 727 . 799 



External characters with internal characters only 532 .669 



Internal characters with all characters S^^S -^57 



Internal characters with internal characters only 383 .595 



A preliminary inspection of these tables shows that the degrees 

 of correlation are relatively high throughout. Many of the coeffi- 

 cients exceed .9 and the lowest is .38. Again we find the two sexes 

 entirely separate with respect to the degrees of correlation. The 

 females show markedly higher degrees of correlation than the 

 males, there being in 66 cases only three in which the coefficient 

 is lower in the female. In two of these exceptions the observed 

 difference is less than the probable error. These differences 

 disappear in the averages of course so that considering each char- 

 acter with reference to all the others we may say that the females are 

 uniformly more perfectly correlated than the males. The average 

 coefficients for all characters are .727 — males and .799 — females; 

 that is, the female coefficients are 10 per cent higher than those of 

 the males. It will be recalled that the females were also about 23 

 per cent more variable than the males so that the more variable sex 

 IS at the same time the more perfectly correlated: a high degree of 

 variability being associated here with a high degree of correlation. 



Again we find that the characters measured fall into two quite 

 distinct groups with respect to their coefficients of correlation 

 much as with respect to their coefficients of variability. All of 

 the external dimensions together with total weight and weight of 

 gastrocnemii form a fairly uniform group and show a much higher 

 degree of correlation than do the weights of liver and ovaries and 

 length of alimentary canal, which form another distinct group. 

 Table XIX summarizes these relations and shows the average 

 coefficients of correlation of the "external" characters among 

 themselves to be .837 — male, and .912 — female, while the "inter- 

 nal" characters among themselves give only .383 — male and .595 — 

 female. The average coefficients of external characters with 



