Epimorphosis

[4] Epimorphosis regeneration can be observed in both vertebrates and invertebrates such as the common examples: salamanders, annelids, and planarians.

[5] Thomas Hunt Morgan, an evolutionary biologist who also worked with embryology, argued that limb and tissue reformation bore many similarities to embryonic development.

[6] Building off of the work of German embryologist Wilhelm Roux, who suggested regeneration was two cooperative but distinct pathways instead of one, Morgan named the two parts of the regenerative process epimorphosis and morphallaxis.

Specifically, Morgan wanted epimorphosis to specify the process of entirely new tissues being regrown from an amputation or similar injury, with morphallaxis being coined to describe regeneration that did not use cell proliferation, such as in hydra.

[7] The key difference between the two forms of regeneration is that epimorphosis involves cellular proliferation and blastema formation, whereas morphallaxis does not.

[13] As the MMPs are secreted, the wound epithelium thickens[13]and eventually becomes an apical ectodermal cap (AEC) that forms on the tip of the stump.

[17] The American cockroach is capable of regenerating limbs that have been damaged or destroyed, such as legs and antennae, as well parts of its compound eye.

All of the Hox genes concerned in epimorphosis are present in the abdominal area of the worm, but not in the anterior portion.