Endocytic mechanisms of the digestive cells of Hydra viridis. 1. Morphological aspects.

The endocytic mechanisms of the digestive cells of Hydra viridis were examined by transmission electron microscopy. Algae which form a stable intracellular symbiosis are phagocytosed by uncoated plasmalemma, as are large (greater than 0.5 micron) food particles. Discoidal coated vesicles apparently effect the endocytosis of smaller particles, including macromolecules. Competition experiments indicate that the uptake of algae and larger food particles utilize similar endocytic membrane.