It is now known that the “gills” that supposedly appear in the early stages of the human embryo are in fact the initial phases of the middle-ear canal, parathyroid, and thymus. That part of the embryo that was likened to the “egg yolk pouch” turns out to be a pouch that produces blood for the infant. The part that was identified as a “tail” by Haeckel and his followers is in fact the backbone, which resembles a tail only because it takes shape before the legs do.