LENGTH OF THE INTERNODES 



33 



1. Correlation of the Length and Diameter of the In- 

 ternode from a slngle locality in a glven frog 



In order to see whether or not the length of the internode is 

 correlated with the diameter, I have determined the coefficient of 

 correlation between the two characters just mentioned in each 

 group from the formula given below 



1 



71 / a, a, 



(see Davenport's Statistical Methods, 1904) and obtained the fol- 

 lowing results: 



GROUP 1 



Coeffi- 

 cient 



of cor- 

 relation 

 or r =: .0797 ±.0535 



GROUP 2 



0.1947 ±.0195 



GROUP 3 



0.1480±.0169 



GROUP 4 



.3399 ±.0242 



GROUP 5 



.3456 ±.01 36 



In every case the coefficient of correlation is positive and is 

 greater than the corresponding probable error. We therefore 

 consider that the diameter and the length of the internode are 

 certainly correlated. Though the degree of correlation is never 

 high, nevertheless we can say positively that so far as the present 

 data are concerned, the longer internode is associated with larger 

 diameter in the values given in each group, and vice versa. 



We also noticed in the above table that in general the degree 

 of correlation becomes greater as the animal becomes larger. 

 In another trial we have obtained from Takahasi's data (measure- 

 ments from sciatic in thigh only) a coefficient of correlation as 

 high as 0.6681, his observations having been made on large frogs 

 (body weight 26 to 63 grams). Since during the period of rapid 

 growth the relation between the two characters must be more 

 irregular, it follows that the degree of correlation would be less 

 in the young than in the adult. Therefore the view maintained 

 by the earlier investigators that "the length of the internodes 



