RELATIVES ON THE SUPPOSITION OP MENDELIAN INHERITANCE. 423 
21. We shall use this formula for the fraternal correlation to estimate the relative 
importance of dominance and environment in the data derived from the figures given 
by Pearson and Lee. 
Assuming as the observed correlations 
Stature. 
Span. 
Cubit. 
n . 
. -2804 
•1989 
T977 
V • 
. -5066 
•4541 
■4180 
/ • 
•5433 
•5351 
•4619 
we obtain as before 
c i c 2 
. -7913 
•7575 
•6980 
A . 
•2219 
•1507 
•1377 
and calculating Cp from the formula 
Cl = 4/-c lC2 (l + 2A), 
we obtain the three values 
1-031 1-155 -957 
with a standard error of ‘072, and a mean of 1‘048. 
This relatively large standard error, due principally to our comparative ignorance 
of the fraternal correlations (errors in m have scarcely any effect, and those in p 
are relatively unimportant), prevents us from making on a basis of these results 
a close estimate of the contributions to the total variance of the factors under 
consideration. 
Remembering that c\ is intrinsically less than unity, the second value is 
inexplicably high, whilst the first and third are consistent with any value sufficiently 
near to unity. The mean of these results is materially greater than unity, and 
therefore gives no support to the supposition that there is any cause of variance in 
these growth features other than genetic differences. If this is so, we should put 
c\ = 1, and compare the observed values of /with those calculated from the formula 
4/=l + c 2 (l + 2A). 
With their standard errors we obtain 
Stature. 
Span. 
Cubit. 
Standard Error, 
Observed 
■5433 
•5351 
•4619 
•016 
Calculated 
•5356 
•4964 
■4726 
•008 
Difference 
. - -0077 
-•0387 
+ •0107 
•018 
The exceptional difference in the fraternal correlations for span might, perhaps, 
be due to the effects of epistacy, or it may be that the terms which we have neglected, 
which depend upon the finiteness of the number of factors, have some influence. It 
is more likely, as we shall see, that the assumption of direct sexual selection is 
TRANS. ROY. SOC. EDIN., VOL. LII, PART II (NO. 15). 65 
