408 
Study of Blood Corpuscles of Tadpole 
There appeared thus to be a significant difference and on drawing the regression 
line, it was at once seen to be curved : see Diagram II. 
The facts that the length of the corpuscle decreases with the growth of the 
tadpole, and further that the correlation between length and breadth is not very 
marked and is not linear, render it hard to obtain any character of the blood 
corpuscle free from growth changes. 
Diagram II. i?. ieHipono-ia Tadpoles. Regression of Breadth on Length of Corpuscle. 
4-0 
5^)5 5^5 5-95 6-J5 ?75 tl5 7^55 7-95 8-35 SV5 9^/5 9-55 9-95 m-35 l(-75 12' 15 
Length of Corpuscle. 
The diagram shows the badness of fit of the I'egression line AB, and the 
improvement of fit when we adopt the regression parabola ODE*, or: 
where /S., are the usual biometric functions of the moments, and (Xy the 
standard deviations, x, y the means of the lengths and breadths of the corpuscles. 
In the present case the equation to this parabola referred to the mean as 
origin is : 
F=-270X--109Z-+-094. 
In judging of the fitness of the parabola no weight can be given to the means 
of the first and last few arrays, which contain very small numbers of corpuscles ; 
* Pearson : "On the General Theory of Skew Correlation," Drapers'' Retsearch Memoirs (Dulau & Co.), 
p. 29. 
