FIGURE 2 | Selected examples of Haeckel's diagrams of comparative embryo stages.

From the following article:

Gavin Rylands de Beer: how embryology foreshadowed the dilemmas of the genome

Tim J. Horder

Nature Reviews Genetics 7, 892-898 (November 2006)

doi:10.1038/nrg1918

Gavin Rylands de Beer: how embryology foreshadowed the dilemmas of the genome

On the basis of evidence such as these diagrams, Ernst Haeckel controversially20, 21 argued that early embryo stages (top row) shared similar, although evidently not identical, features (as earlier noted by Karl Ernst von Baer), and that these represented the recapitulation of ancestral adult forms. So, for example, all vertebrates seem to go through a fish-like stage. This mechanism offered the tantalizing prospect of access to what is, in effect, a direct record of steps in evolution. In the absence of even a basic understanding of genetics, Haeckel believed that: "...phylogenesis is the mechanical [that is, mechanistic] cause of ontogenesis."17 By giving causal priority to embryological mechanisms, de Beer would reverse this formula by arguing that changes in ontogeny were the cause of phylogenetic change. Reproduced with permission from Ref. 17 © (1910) Rationalist Press Association.

Download file

If the slide opens in your browser, select "File > Save As" to save it.