On Mendels Laws. 
199 
for either race taken separately, and yet the mixture would exhibit 
an apparent heredity due simply to the constancy of type for each 
race. It would be true for the mixture that the taller parents 
had the taller offspring, but not true for either race separately. The 
same thing holds good in the case of attributes. If two races be 
mixed, of which a large per-centage of individuals in the one case 
and only a small per-centage in the other, possess some attribute, 
it will be true for the mixture that the offspring of A’s 
exhibit a larger proportion of /l’s than the offspring of a’s ; but this 
will not necessarily be true for either race separately. The two 
classes A and a belong, I take it, to one race when pure matings of 
of A’s with A’s may give rise to a's and vice-versa. In the case of 
a continuously-variable character, all the individuals may be held to 
belong to one race if they cannot be divided into two classes such 
that pure matings between members of the one class never give 
rise to offspring that would be assigned to the other. The dis¬ 
tinctions between continuity and discontinuity of variation, between 
inheritance of attributes and of variables do not seem to me to be 
of necessary importance for the theory of heredity; successive 
discontinuities may be so slight as to be undiscoverable by the 
most careful and repeated measurements. The real and important 
distinction seems to lie between the phenomena of heredity within 
the race, and the phenomena of hybridisation that occur on crossing 
two races admittedly distinct. Several of the investigations of Mr. 
Galton relate to the inheritance of attributes (eg. of temper, of 
artistic faculty in man, of colour in Basset-hounds), none of them 
(so far as I am aware) to hybridisation. It does not seem probable 
that either he or Professor Pearson intended the term heredity to 
cover such cases; I can certainly say for myself that in stating any 
rule to be a “ law of heredity,” I should not dream of implying 
thereby that it was a law of hybridisation. 
Mr. Bateson fails to make any distinctions whatever. Mr. 
Galton’s researches on Basset-hounds and the Galton-Pearson work 
on eye-colour in man (both referring to individual heredity within 
the race) are classed, under the general heading of “discontinuous 
variation,” with Mendel’s work on crossing distinct races of peas 
and Mr. Bateson’s own on hybridisation of flowers and races of 
poultry, as if they referred to compaiable matter. This does not 
tend to clearness. Mr. Bateson further adduces the work of 
lnjbridisers to rebut the generality of the Galton-Pearson law of 
heredity :— 
