Protonephridia.
D000818:Animals; D004446:Echinococcus / Q000502:physiology; D005209:Fasciola / Q000166:cytology; D005210:Fasciola hepatica / Q000166:cytology; D007448:Invertebrates; D010986:Platyhelminths / Q000166:cytology* / Q000502:physiology; D014882:Water-Electrolyte Balance