98 
PROFESSOR K. PEARSOX AXD DR. A. LEE OX 
Table III., are as a rule larger than the probable errors of the differences, sometimes 
several times larger. Yet in some cases they are not such large multiples of the 
probable errors of the differences that we can afford to lay great stress on the 
divergence of g or £ or u in a pair of special cases. We must lay weight rather on 
the general tendency of the tables when all the series are taken together. Thus, 
while we may have small doubt about the correctness of (i.) of § 7 or ( b ) of § 8, we 
should look upon (iv.) of § 7 as an important suggestion which deserves serious 
consideration rather than a demonstrated law. The same again holds good for (c) of 
§ 8. It is because of their suggestiveness that they are here included. That a 
differential fertility or an individualisation in the sex of offspring should be corre¬ 
lated with colour, would, if proved, be a fact of very considerable interest. It would 
again emphasise the important part which genetic selection plays in the modification of 
characters. # A priori it is not more unreasonable to expect coat-colour in horses than 
to suppose hair-colour in men to be correlated with fertility. But the fertility of man 
does seem to vary from the light to the dark races. The special feature of interest 
here, however, is that a different colour in the two sexes appears to influence the 
preponderance of one or other sex in the offspring. It would be an interesting 
inquiry to determine whether the sex-ratio in the offspring of “ mixed marriages ” 
varies when the races of the two parents are interchanged. 
(9.) On the Inheritance of Coat-colour in Thoroughbred Horses. —(a.) Direct Line. 
First Degree. —Having regard to the probable errors—about ‘03 —in the values of 
the correlation coefficient r xyi it seems quite reasonable to suppose that the mean 
parental correlation, actually '5216, is practically '5. It is quite impossible to 
imagine it the '3 of Mr. Galton’s view of the Law of Ancestral Heredity. If we 
adopt the view of that law given in my paper on the Law of Ancestral Heredity,! 
and take the coefficient y to be different from unity, then it is shown in my paper on 
the Law of Reversion! that we cannot on the theory of blended inheritance get 
parental correlation as high as '5 without values of the fraternal correlation which 
are much higher than those hitherto observed, certainly much higher than, as we 
shall see later, we find in the case of coat-colour in horses. Coat-colour in horses does 
not thus appear to be at all in accord with Mr. Galton’s view of ancestral inheritance, 
or even with my generalised form of his theory. It does accord very well with what 
we might expect on the theory of exclusive inheritance as developed above, p. 91, 
on the assumption that there is no reversion. 
Looking at the matter from the relative standpoint, we see that not much stress can 
be laid on the respective influences of the sire and dam on the colt, or of the sire and 
dam on the filly ; but, on the other hand, the filly does appear to inherit more from 
* See the concluding remarks in the memoir on “ Genetic (Reproductive) Selection,” ‘ Phil. Trans.,’ 
A, vol. 192, pp. 257—330. 
t ‘ Roy. Soc. Proc.,’ vol. 62, p. 386 et seq. 
1 ‘Roy. Soc. Proc.,’ vol. 66, p. 140 et seq. 
