TO THE THEORY OF EVOLUTION. 
39 
The quadratic gives r = ’2237. Using the Newtonian method of approximating to 
the root we find 
r = '2222. 
Summing up as before, after finding the probable errors, we have 
h = k = -3190 ± -0133, 
r = -2222 ± -0162. 
Illustration IV. Inheritance of Eye-colour in Man .— To find the correlation in 
eye-colour between a maternal grandmother and her granddaughter. Here the 
classification is into eyes described as grey or lighter, and eyes described as dark grey 
or darker * 
Tint. 
Maternal grandmother. 
Totals. 
Grey or lighter. 
Dark grey or 
darker. 
Granddaughter. 
Grey or lighter.... 
254 
136 
390 
Dark grey or darker . . 
156 
193 
349 
Totals. 
410 
329 
739 
As before, we find 
a 1 = -109,607, = -055,480, 
h - -138,105, k — -069,593, 
log HK = 1-196,6267, 
e = -323,760. 
Series for r up to r 4 
•323,760 = r + -004,806r 3 + T62-696r 3 + -000,358?- 4 . 
The quadratic gives r = "3233, and the biquadratic 
r = -3180, 
the value of the term in r 4 being -000,00366, so that higher terms may be neglected. 
Determining the probable errors as in Illustration I., we sum up :— 
* According to Mr*. Galton’s classification, the first group contains eyes described as light blue, blue, 
dark blue, blue-green, grey ; and the second eyes described as dark grey, hazel, light brown, brown, dark 
brown, verv dark brown, black. 
