1897.] General Biology. 1043 
General Notes. 
— 
GENERAL BIOLOGY. 
The average Contribution of each several Ancestor to the 
total Heritage of the Offspring.'—We inherit not only from our 
parents but also from our grandparents to remote generations. The 
problem is: What proportion of the whole is, on the average, inherited 
from each generation ? 
In an earlier work, Galton, as a result of experiments on sweet peas, 
reached the conclusion that 50 per cent. of our qualities are on the 
average derived from our two parents, and he suggested the probability 
that 25 per cent. comes from our four grandparents, 12.5 per cent. from 
all our great-grand-parents, and so on, the sum being 100 per cent. 
thus accounting for the whole inheritance. The present paper brings 
the required proof of Galton’s hypothesis. 
The method of proof is noteworthy. Galton had access to pedigree 
records of ‘ Basset’ hounds bred through twenty years. These exhibited 
only two color types—tricolor (T) and non-tricolor (N). There were 
817 hounds of known color derived from parents of known color: 567 
of these had all four grandparents of known color; and 188, all great- 
parents. Galton determined, for example, whether the proportion of 
T-progeny of a known ancestry corresponds to the law of contribution 
enunciated above. He separated the progeny into three lots; namely, 
those which have 2 T-parents, 1 T-parent or 0 T-parent; each of these 
may be subdivided into lots having 4, 3, 2, or 1 T-grandparent. Do 
the percentages of T-progeny in these lots accord with what we might 
calculate from the law? Let us take acase; there are 119 individuals 
which have 2 T-parents and 3'T-grandparents. What per cent. should 
be tricolor? The two T-parents should each determine 25 per cent. 
total, 50 per cent. Each of the 3 T-grandparents should determine 
+25 per cent., 6.25 per cent., total 18.75 per cent. together 68.75 per 
cent. To this must be added the influence of the T-great-grandparents 
and earlier ancestors. The probable percentage of unobserved T- 
ancestors and hence of T. -generating influence may be calculated on the 
assumption that the percentage ¢ of T-parents producing T or N progeny 
will be the same for unknown as for known generations. By an exten- 
' Francis Galton: Proc. Royal Soc. lxi, p. 401-413, 1897. 
