This video lecture from Homeostasis (F.Sc. second year Biology) covers: Excretion in Hydra and Planaria - In simple organisms like hydra, waste material move out by simple diffusion while in planaria excretory system is present i.e. flame cell excretory system (protonephridium). Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.