flatworm found on a coral in saipan while diving

flatworm worm white animal planaria isolated biology background vector structure scheme physiology schema anatomy system morphology nature planarian flat nerves water nervous excretory closeup zoology turbellaria tube cell gastrovascular urinary nephridium platyhelminthes protonephridia predator flame ganglia microscopic nephridia macro cilia protonephridium secretory ovary testes gonopore female seminal vesicles reproductive found coral saipan diving bright