1184 THE STRUCTURE OF EVOLUTIONARY THEORY
when we place his biological views into the context of evolutionary debate in his own
time, we find, underneath his quirky stylistic uniqueness, a standard critique of
Darwinism based upon the common argument that natural selection cannot fashion
novel features, but can only eliminate the unfit, bolstered by a claim for saltation as a
common mode in the origin of highly distinct taxa and anatomical groundplans.
D'Arcy Thompson did link this standard critique to an uncommon solution—his
central claim that physical forces shape adaptive form directly—but we should regard
his theory as an unusual solution to the standard conundrums of his time, and not as
an anachronistic importation from Pythagorean Greece, clothed in the prose of
Dickens or Thackeray.
On Growth and Form is a weighty tome (793 pages in the original edition of
1917, enlarged to 1116 pages in 1942), but D'Arcy Thompson presents his central
thesis as a tight argument, expressed in clear logical order, with proper attention to
inherent difficulties—and, above all, artfully developed throughout. (My analysis
here, with two labeled exceptions, follows the first edition.)
In a common conceit (in the non-pejorative sense of a fanciful device), scientists
often clothe a truly radical idea in the falsely modest garb of merely useful
technicality. Thus, D'Arcy Thompson asserts that he wrote Growth and Form only to
make biologists a bit more comfortable with the mathematical description of
morphology. He states in his epilog (1917, p. 778):
The fact that I set little store by certain postulates (often deemed to be
fundamental) of our present-day biology the reader will have discovered and I
have not endeavored to conceal. But it is not for the sake of polemical
argument that I have written, and the doctrines which I do not subscribe to I
have only spoken of by the way. My task is finished if I have been able to
show that a certain mathematical aspect of morphology, to which as yet the
morphologist gives little heed, is interwoven with his problems,
complementary to his descriptive task, and helpful, nay essential, to his proper
study and comprehension of Form. Hie artem remumque repono. *Beginning his assault upon biological traditions of explanation, D'Arcy
Thompson reminds us that we feel no discomfort in ascribing the elegant and well-
fitting forms of inorganic objects to physical forces that can mold them directly, and
that also embody the advantage (for our comprehension) of simple mathematical
description. Why, then, when organic forms display equally elegant and simple
geometries, and when these biological shapes also match the expected impress of
physical forces, do we shy from invoking the same explanation of direct production
that we apply without hesitation to identical forms in nonorganic nature? (1917, pp.
7 - 8):
- D'Arcy Thompson couldn't resist a frequent Latin (or Greek, or Italian, or French, or
German, or whatever) quotation, always untranslated. This little paragraph-ending phrase
continues his theme of false modesty by proclaiming: At this point I close my composition
and put back my oar.