124 BLASTOGENIC VAEIATIONS. 



tributes on an average one-quarter, or (0.5) 2 , each 

 grandparent one-sixteenth, or (0.5) 4 , and so on, or that 

 the occupier of each ancestral place in the nth degree, 

 whatever be the value of n, contributes (0.5) 2n of the 

 heritage. 



It is unnecessary to quote the numerical details ad- 

 duced by Galton, but two final results may be men- 

 tioned just to show how close was the approximation be- 

 tween fact and theory. Thus in one series 387 tri- 

 colour offspring were obtained from certain parents of 

 known colour, themselves the offspring of parents of 

 known colour. On the law of heredity, the number of 

 tricolour offspring should have been 391. In the 

 other series, the colours of the great-grandparents were 

 known in addition, and in this case the approximation 

 was even closer. One hundred and eighty-one tri- 

 colour offspring were obtained, as against the calculated 

 number of 180. 



Galton points out that there is nothing in his statis- 

 tical law to contradict the generally accepted view that 

 the chief, if not the sole, line of descent runs from germ 

 to germ, and not from person to person. The person 

 on the whole may be accepted as a fair representative 

 of the germ, and so statistical laws which apply to per- 

 sons would apply to germs also. Now the law is 

 strictly consonant with the ' observed binary subdivi- 

 sions of the germ cells, and the concomitant extrusion 

 and loss of one-half of the several contributions from 

 each of the two parents to the germ cell of the off- 

 spring. 



Galton's law has been shown by Pearson * to be even 

 *Proc. Roy. Soc., Ixii. p. 386, 



