The Fruitful Facets of Galton's Polyhedron 459
false and detrimental to his influence—became the chief obsession of
Goldschmidt's old age).
- Material Basis grants the developmental theme a clear prominence in both
place and space. In his introductory pages, Goldschmidt complains that
evolutionary thought suffers by disregarding a vital subject: "There is, finally,
another field which has been neglected almost completely in evolutionary
discussions; namely, experimental embryology. The material of evolution consists
of hereditary changes of the organism. Any such change, however, means a
definite change in the development of the organism" (pp. 5-6). "A change in the
hereditary type can occur only within the possibilities and limitations set by the
normal process of control of development" (p. 1).
Presentation of the Chart for Macroevolutionary Distinctiveness
evolutionary method" behind the origin of species—cobbles two strikingly
different discussions together: the first (pp. 184-250) on systemic mutation and the
non-existence of the "corpuscular gene"; and the second (pp. 250-396) on
constraints and opportunities of developmental systems, and the potential
macroevolutionary consequences of mutations affecting early development.
Goldschmidt strongly emphasized the second discussion (at more than twice the
length devoted to the first theme). Moreover, he situated his entire treatment of
hopeful monsters (pp. 390-393) within the developmental section. In the opening
paragraph on hopeful monsters, Goldschmidt lists his favorite potential
examples—concrescence of tail vertebrae to produce a fanlike arrangement of
feathers in ancestral birds, the passage of both eyes to one side of the head in
flatfishes, and an achondroplastic bow-legged dog that ranks as a mere monster
until humans need to extract badgers from dens and therefore breed dachshunds.
Goldschmidt interprets these examples entirely in terms of small mutations
affecting early development. He states, following the citation of dachshunds (p.
391): "Here, then, we have another example of evolution in single large steps on
the basis of shifts in embryonic processes produced by one mutation... This basis
is furnished by the existence of mutants producing monstrosities of the required
type and the knowledge of embryonic determination, which permits a small rate
change in early embryonic processes to produce a large effect embodying
considerable parts of the organism."
- The developmental theme pervaded Goldschmidt's career, in both duration
of work and centrality of focus. I mentioned above (p. 453) that Goldschmidt
centered his empirical studies upon the gypsy moth, Lymantria dispar. His
voluminous research on the genetics of geographic variation, published under the
collective title Untersuchungen zur Genetik der geographischen Variation,
convinced him that diversification within species, though Darwinian and adaptive,
did not lead to the origin of new species. But Goldschmidt pursued a second line of
work on Lymantria for more than 20 years and through equally voluminous
publication—studies on sexual determination and intersexuality (culminating in a
long series of papers collectively titled, Untersuchungen iiber Intersexualitat).
In these developmental studies, Goldschmidt recognized normal sexuality