In open circulatory system, the blood flows in open spaces like lacunae and sinuses and it bathes the cells directly, e.g., arthropods (cockroach or Periplaneta). Octopus and Sepia are the cephalopods in which the circulatory system is of completely dosed type. Pheretima and Hirudinaria are the annelids. Annelids possess the closed circulatory system in which the blood circulates inside the blood vessels without coming in direct contact of body cells.