MENDELISM AND BIOMETRY 229 
horses, which would have been classed unhesitatingly 
as instances of heredity by all biometricians in Igoz. 
Bateson’s instinct did not fail him when he divided 
these problems into those of continuity and those of 
discontinuity respectively, although at the present time 
the realm of continuous variation and inheritance is 
being steadily encroached upon owing to the analysis 
of complex characters into definite constituents. 
In 1904 Karl Pearson struck a blow at the prospect 
of conformity between biometrical and Mendelian 
results in his memoir, ‘On a Generalized Theory of 
Alternative Inheritance, with special reference to 
Mendel’s Laws.’ Pearson’s treatment of the subject 
involved advanced mathematical reasoning, and we 
can, therefore, only give a brief summary of his main 
results. Pearson proposes special terms for the A and 
the a elements respectively of a couplet or pair of 
allelomorphs. He proposes to call the A element a 
protogene, and the a element an allogene, and he thus 
distinguishes between the two sorts of homozygotes 
by calling AA a protozygote and aa an allozygote. 
Pearson considered the case of a population breeding 
together at random, in which a single measurable 
character, suchasstature, is determined by the combined 
action of an indefinite number of pairs of allelomorphs, 
and he proceeded to work out the value of parental 
correlation which was to be expected under these 
circumstances. This value he found to be exactly 
one-third, a value which happens to be identical with 
Galton’s original determination of parental correlation 
from his statistics of human stature. A considerable 
