title: The principle of non-equivalence in development.
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002454:Cell Differentiation; D002642:Chick Embryo; D005552:Forelimb / Q000196:embryology; D006614:Hindlimb / Q000196:embryology; D007313:Insecta; D009024:Morphogenesis; D009046:Motor Neurons; D009132:Muscles / Q000294:innervation; D009434:Neural Pathways; D011894:Rana pipiens; D012038:Regeneration; D012867:Skin / Q000196:embryology / Q000294:innervation