EVOLUTION 



479 



portance of this law of ancestral heredity. If Darwinism 

 be the true view of evolution, i.e. if we are to describe 

 evolution by natural selection combined with heredity, 

 then the law which gives us definitely and concisely the 

 type of the offspring in terms of the ancestral peculiarities 

 is at once the foundation-stone of biology and the basis 

 upon which heredity becomes an exact branch of science. 

 To show its importance, let us draw some of the con- 

 clusions which follow from it. Let us suppose that mating 

 is pangamic, that the race is sensibly stable, and that the 

 two sexes are equipotent in determining the character of 

 the offspring, the heritage being equally blended. Then 

 we have seen that the quantities by which the H's are 

 multiplied can be expressed in terms of the correlation co- 

 efficients of the offspring and the mid-parents. These 

 latter can be again expressed in terms of the correlation 

 coefficients between the offspring and the individual 

 ancestry, and from the resulting equations the intensity 

 of heredity between every possible pair of relatives deter- 

 mined. The actual algebraic deductions are too complex 

 to be reproduced, but the results are so important that 

 they may be given here : — 



Table of Heredity — Direct Line. 



The first column contains what I have previously 

 termed the " theoretical values " of the coefficients of 

 heredity. So far as our data at present reach, — and 



