Fig. 1

Haeckel’s famous depiction of his biogenetic law, or recapitulation theory. The upper row is representative of early development, the middle row of mid-development, and the lower row of late development. Using the labels used by Haeckel, the embryos represented include: F fish, A salamander, T turtle, H chick, S pig, R cow, K rabbit, and M human. Figure from Anthropogenie by Haeckel (1874)