Fig. 3. Modes of germ cell specification across the Metazoa. Boxes refer to modes of germ cell specification as described in the existing literature: red, epigenesis; blue, preformation; half red, half blue, groups in which some species show preformation and others epigenesis; white, no data. Asterisks indicate phyla in which epigenesis has been claimed, but recent data suggest preformation (see discussion in main text). Phylogeny is modified from Peterson and Eernisse (Peterson and Eernisse, 2001), but many relationships within the Ecdysozoa and Lophotrochozoa remain unresolved by molecular data (Adoutte et al., 2000). The phylogenetic positions of the Chaetognatha and Gnathostomulida are particularly uncertain (dotted lines).

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