II

Such was the general condition of theoretical biology about the
beginning of the present century. In the meantime those who were dealing
with the empyrical or experimental side of these problems were seeking
for the causes of and the rules for variation. All living things vary
from one generation to another; the question was, Why do they vary? and
do these variations really represent new characters comparable to new
species in the making? or are they, so to speak, but an elastic reaction
of the internal vital elasticity of the organism, all the while latent
and only seeking a favorable expression, to return again under other
conditions to the former type?

The effort to reduce these variations to law and system was pursued by
thousands of investigators, with varying but at all times perplexing
and disappointing results. But in the year 1900 the scientific world
awoke to the surprising fact that a patient obscure investigator had
already solved most of the puzzles of variation and heredity some
thirty-five years before. Gregor Mendel, born a peasant boy, trained as
a monk, and afterwards appointed Abbot of Brünn, had in the year 1865
published the results of his experiments in breeding, which had been
ignored or forgotten until rediscovered in 1900 by de Vries and two
others simultaneously. From this point Mendelism, as it is now called,
has steadily gained ground, until at the present time it can be said to
be the dominating conception among biologists the world over regarding
the problems of heredity.

Mendel worked chiefly with peas, crossing different varieties. In his
methods of investigation he differed from all previous investigators in