J. Cartledge

Leporid Natural History

Measuring Shells (for Gould)


two-color lithograph with hand-tinting

18" x 25"

Measuring Shells (for Gould) – This image is based on a 1971 paper by Stephan Jay Gould, in which he observed that two different species of snails, one large and one small, had evolved over time into the same medium size and the exact same shape. Gould discovered that while selection accounted for the gradual move to medium size, the similarity in the shape of the shells was due to the fact that there was only one way, structurally, for the shells to achieve a medium size – by taking on the same shape. For those interested, the numbers on the blackboard represent the ratio of height to width in the sample shells (k-value), the shape of samples Gould collected in Bermuda, and the progression of height and width of two different sized individual snails.