nervous, reproductive, digestive and excretory system of planaria flatworm

anatomy animal background biology cavity cell cilia digestion digestive excretory female flame flatworm ganglia gastrovascular gonopore illustration isolated male morphology nephridia nephridium nerves nervous ovary part pharyx physiology planaria protonephridia protonephridium reproductive schema scheme secretory seminal set structure system testes tract tube urinary vector vesicles white worm