256 Raphael Falk
cles were somehow representatives of the characteristics into which they develop
(Entwickeln –unfold in German). Thus when A. K. Darbishire’s hybridization
experiments with mice in England [Darbishire, 1902], and William E. Castle’s ex-
periments with rats in the United States showed unexpected variation in fur color
of the progeny of hybridization experiments [Castle, 1906], the discreteness of the
MendelianFaktorenwas challenged. William Castle recounted:
My own experimental studies of heredity, begun in 1902, early led me
to observe characters which were unmistakablychangedby crosses and
so I have for many years advocated the view that the gametes are not
pure in the sense expressed by Bateson. [Castle, 1919a, 126]It was, however, the Danish pharmacist Wilhelm Johannsen who made the next
critical step in conceptually setting apart traits, thephenotype, as the markers of
somethingwhich is the inherent essence needed for traits, thegenotypeand its
discrete entities, thegenes[Johannsen, 1909]. Johannsen nourished a typologist
conception. His problem was to settle the conflict between a normal or binomial
distribution of the quantitative traits that he studied and the notion of a distinct,
discreet Aristotelian type. Johannsen’s answer was briefly that characters (the
phenotype) vary continuously but heredity (the genotype) varies discontinuously
[Roll-Hansen, 1978]. As a phenomenologist, but not a positivist, he came forward
with hypotheses that allowed him to “analyze” [Provine, 1971, 95] Galton’s and
later his own quantitative data beyond the statistical presentation, and to suggest
that Galton’s partial regression to the mean was due to the initial mixture of es-
sential (geno-)types in the population. In his bean experiments he easily picked
out (after little inbreeding) such types, or “pure lines” in each of which regression
to the mean of the type was complete. As a follower of Pearson’s phenomenol-
ogy Johannsen conceived of the genotype as the quantitative correspondent to the
phenotype, being “the type beyond the average” [Falk, 2000b, 320]. The result of
analytical experiments in genetics is “the upsetting of the transmission conception
of heredity... The personal qualities of any individual organism do not at all
cause the qualities of its offspring” [Johannsen, 1911, 130-131]; The observable
characteristics of individuals are the responses caused by the type which is inher-
ited. Accordingly, Pearson was referring to phenotypes, whereas Bateson used the
phenotype as the referent to the invisible genotype. The phenotypes of traits that
segregated as Mendelian unit characters were “markers” or sign poles of the units
of the genotype, namely of thegenes. But by the term gene “merely the simple no-
tion should be expressed thatsomethingin the gametes has or may have properties
that condition or take part in the determination of a property of the developing
organism. No hypothesis on the existence of this ‘something’ should therewith
be construed or supported” [Johannsen, 1909, 124]. Johannsen never committed
himself to the nature of these genes, whether they wereintervening variableor
hypothetical constructs[MacCorquodale and Meehl, 1948]; this, however, became
a major issue in the years to come [Falk, 1986].
As noted, Mendelselected traits that display two qualitative different forms.