The Fruitful Facets of Galton's Polyhedron 375
5 - 5. Hyatt's phylogeny for the Steinheim planorbids could not differ more from Hilgendorf's.
Hyatt envisages several parallel lineages each in different stages of the same phyletic life cycle,
with some lineages becoming stronger (as expressed in their larger and thicker shells) and others
becoming evolutionarily senile in their thinner, smaller, and irregularly coiled shells. This
interesting figure comes from a glass plate that Hyatt prepared for his 1880 monograph but did
not publish. The printed version is much cruder and less informative. I here publish Hyatt's
original for the first time. (I now occupy his office and I found this plate in the drawer that still
contains his Steinheim specimens.) The three rightmost lineages represent three sub lines of a
single degenerating stock, hence giving four lineages in toto (as the text states).