Alexander O. Kowalevsky (1840–1901), a founder of cellular and comparativeevolutionary embryology, was one of the most prominent biologists of thenineteenth century. He worked at the intersection of zoology, embryology, andevolution. His studies on the lancelet, tunicates, insects, and germ layer homol-ogies pioneered comparative embryology and confirmed the evolutionary conti-nuity between invertebrates and vertebrates. In this chapter I present a shortdescription of the life of A.O. Kowalevsky and his achievements and, withtheir help, illustrate the development of comparative evolutionary embryologyin the last third of the nineteenth century. The chapter also presents the fullbibliography of Kowalevsky.