Biologist used to say that "ontogeny recapitulates phylogeny" an
invertebrate taxonomist that I know says "no more" . But I don't know why.
Ontogeny being the stages in embryonic development and phylogeny the
stages in evolutionary development. For instance: a developing embryo
resembles a fish at one point because it has gill slits and at another
stage an amphibian, both susposed stages in the evolutionary development