The source of cells for regeneration.
D000557:Ambystoma / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation; D005121:Extremities / Q000473:pathology / Q000502:physiology; D008679:Metaplasia; D010932:Planarians / Q000166:cytology / Q000502:physiology*; D012038:Regeneration; D014419:Turbellaria / Q000502:physiology*