doubts that natural selection could explain the colors of insects or the shapes of leaves and horns. There were doodles of aeroplane and dragonfly wings, honeycomb, cell shapes, and bone structures. There were lists of numbers and sketched graphs and a correspondence with A. C. Aitken at the University of Edinburgh over some data D’Arcy had collected on the allometry of the stag beetle’s body parts. (“What is interesting in your sample is the disproportionate growth at different ranges of size—the larger beetle is not a magnification of the smaller one,” Aitken wrote.) There was speculation on diversity, from one of D’Arcy’s book reviews: “We begin by marvelling at the wealth of species in the world, and end by realizing that, in contrast to infinite variety, they are very few.” There was a letter of warning from Marcus Hartog, a leading cell biologist of the late nineteenth century: “I would advise you to be on your guard against the physicists: they love to simplify the problem out of all real relation to the facts of the organism.”
Connections emerged; degrees of separation shrank. A quote from Alexander von Humboldt on the physiology of electric fish had been typed up and pasted into a notebook. Evelyn Hutchinson’s review of the second edition of On Growth and Form was stuck into Thompson’s own copy (“Sir D’Arcy still seems to us fresh from conversation with Aristotle, and still seems to have discussed his material with Galileo”). The editor of Nature had written, asking Thompson to adjudicate on whether a recent paper published in the journal by the Italian mathematician Vito Volterra had reproduced work already published by Alfred Lotka: “Volterra hasn’t got a leg to stand on,” D’Arcy concluded. The theorem, which models the effect that predators have on the numbers of their prey, and vice versa, is now called the Lotka-Volterra equation. A paper cut out of a 1936 edition of Nature suggested that Costa Rica’s plant diversity was due to its high mountains exposing species to mutation-causing cosmic rays.
But yet again, the diversity of ideas and information threatened to become unmanageable. There were notes on the size of nitrogen atoms and comparisons of the size and density of the sun and Betelgeuse; on liquid crystals and molecular films; papers analyzing the relationship between a violin’s wood and its acoustic properties; comparisons