Synopsis. Allometry designates the changes in relative dimensions of parts of the body that are correlated with changes in overall size. Julian Huxley and Georges Teissier coined this term in 1936. In a joint paper, they agreed to use this term in order to avoid confusion in the field of relative growth. They also agreed on the conventional symbols to use in the algebraic formula: y = bx^α. Julian Huxley is often said to have discovered the “law of constant differential growth” in 1924, but a similar formula had been used earlier by several authors, in various contexts, and under various titles. Three decades before Huxley, Dubois and Lapicque used a power law and logarithmic coordinates for the description of the relation between brain size and body size in mammals, both from an intraspecific, and an interspecific, point of view. Later on, in the 1910s and early 1920s, Pézard and Champy's work on sexual characters provided decisive experimental evidence in favor of a law of relative growth at the level of individual development.

This paper examines: (1) early works on relative growth, and their relation to Huxley and Teissier's “discovery”; (2) Teissier and Huxley's joint paper of 1936, in particular their tacit disagreement on the signification of the coefficient “b”; and (3) the status of allometry in evolutionary theory after Huxley, especially in the context of paleobiology.