1. Lewis, E. B. Agene complex controlling segmentation in Drosophila. Nature 276, 567–570 (1978).
2. Raff, R. A. & Kaufman, T. C. Embryos, Genes, and Evolution (Indiana University Press, Bloomington, 1991).
3. Akam, M., Dawson, I. & Tear, G. Homeotic genes and the control of segment diversity. Development 104 (suppl.), 123–133 (1988).
4. Bateson, W. Materials for the Study of Variation, Treated with Especial Regard to Discontinuity in the Origin of Species (Macmillan, London, 1894).
5. Averof, M. & Akam, M. HOM/Hox genes of Artemia: implications for the origin of insect and crustacean body plans. Curr. Biol. 3, 73–78 (1993).