In Pursuit of the Gene

100 ¨ MENDEL
In the same paper, Mendel also mentioned the work of the German
botanist Max Ernst Wichura, who had seen the same constancy among
progeny of hybrid willows that Mendel had observed in hawkweed. Mendel
speculated that the constancy might in some way be connected with the
process of hybridization, but the mystery remained unresolved. For the remainder
of Mendel’s life, the behavior of Hieracium cast doubt on the beautiful
model in which pairs of hereditary factors were divided in the production
of sex cells and recombined in all possible combinations during the
process of sex conjugation. 50
The choice of hawkweed as an experimental plant was twice cursed.
Not only did it deny Mendel the confirmation of his theories that almost
any other species would have provided, but it had led him to Naegeli in the
first place. After Mendel had become involved with Naegeli, who fed Mendel’s
natural tendency to bear down on a single problem, any hope that
Mendel might have turned back from the long dead end of the Hieracium experiments
was extinguished. Although he never referred to Mendel in his
published articles or in his personal letters, Naegeli’s 1884 tour de force,
Mechanisch-physiologische Theorie der Abstammungslehre, showed that in fact he had
absorbed the key lessons of Mendelism. In this highly influential book,
Naegeli laid out his theory of the “idioplasm,” the bearer of the hereditary
qualities. As in Mendel’s factor theory, every kind of quality was represented
as a rudiment in the idioplasm. Furthermore, like Mendel’s germ
cells containing every possible combination of parental traits, Naegeli posited
the existence of as many kinds of idioplasm as there were combinations
of qualities. Naegeli also noted the difference between visible characters and
underlying hereditary factors, and gave as an example a recessive coat color
reappearing among the progeny of hybrid cats.
In November 1873, Mendel wrote Naegeli for the final time, explaining
that his administrative responsibilities had prevented him from doing
any research for the previous two years. The following spring the reformoriented
Liberal Party passed a series of measures aimed at wresting control
of home and family life from the Church. Among these was a new law,
passed in 1874, that would require monasteries to increase their contributions
to a religious fund used to support Church institutions. In accord
with the provisions of the newly enacted law, on October 10, 1875, the