Occurs inside the cell through cyclosis. It occurs in unicellular organisms which lack circulatory system. In them the cytoplasm show regular streaming movement called cyclosis which helps in the distribution as well as the exit of metabolic byproducts from the body by the process of diffusion.
E.g. Paramecium, Amoeba
Occurs outside the body cell i.e. extracellular fluid that circulates in the body for transport of materials it can be
i. Extra-organismic circulation e.g. water circulation system in which outside water circulates in the body of an organism.
ii. Intra-organismic circulation involves circulation of body fluids. E.g. parenchymal circulation (flatworms), coelomic circulation (round worms), blood vascular system (vertebrates and higher invertebrates from annelida onwards)