"Five of the essays included here were originally presented as part of the proceedings of a symposium convened at the Third International Congress of Systematic and Evolutionary Biology, Brighton, Sussex, England, on July 5, 1985."

The biological basis of homology / V. Louise Roth -- Indirect and direct methods in systematics / P.H. Weston -- The characteristics of ontogeny / A.G. Kluge -- The systematic implications of pollen and spore ontogeny / S. Blackmore and P.R. Crane -- Relations between ontogeny and phylogeny with reference to bryophytes / B. Mischler -- Age-dependent evolution / H.M. André -- Epigenetics / S. L›vtrup.