


LOTSY, CURRENT THEORIES OF EVOLUTION. 391 
the year 1900 experiments on the subject of variability were very 
scarce (a notable exception was H. HOFFMANN), while there were 
endless discussions as to the kind of variability causing evolution: 
Lamarckian or Darwinian, continuous or discontinuous (sporting), 
allsided or orthogenetic etc. 
Even BATESON, who in his book on meristic variation made a 
thorough study of diversity, could not liberate himself from the 
belief that variation could be observed, while it can, of course, only 
be tested by experiment. 
The one who first saw this clearly was not a botanist, but an 
amateur, a manufacturer of silk goods at Lyon: ALEXIS JORDAN, 
who put the question at issue correctly: I see diversity within the 
Linnean species, this diversity is hypothetically called variation, I 
Shall test this hypothesis and see whether it is well or ill-founded. 
We all know that he found it ill-founded, that he could prove that 
all morphologically distinguishable types within the Linnean species 
Draba verna, more than 300 in all, come perfectly true, when grown 
from guarded seed, or, in other words, that Draba verna was not 
a highly variable species, a variable unit, but no unit at all; it turned 
out to be a collection of different units, in regard to which the 
Linnean species had the rank of a genus. 
JORDAN, having moreover to his satisfaction, shown that these 
smaller units did sot vary in a transmittable way, but were subject 
to modification only, called these units, discovered by him, which 
he supposed to be immutable: petites espèces, mikrospecies. 
This was unfortunate, then by so doing, he sanctioned, to a certain 
extent, the Lianean species-concept and gave the impression that 
his units were of less worth. He should boldly have called his 
constant forms species, because the orthodox Linnean species- 
concept is the pure line concept and nothing else, and JORDAN’s 
mikrospecies were the first experimentally tested pure lines. 
The fact that JOHANNSEN could show, by means of modern 
methods, many years later, that within morphologically similar 
forms, still smaller pure lines can be distinguished, does not do away 
with the fact, that it was JORDAN, who first logically applied the pure 
line principle, to wit: to sow the guarded seed of a single type 
and that it was he, who, from the results obtained, drew the con- 
clusion that such pure lines were immutable. 
