The circultory system is of two types,
1. Open type: The blood remains filled in tissue spaces due to the absence of blood capillaries.
Eg: Arthropods, Molluscs, Echinoderms, and Urochordates
2. Closed type: The blood Is circulated through blood vessels of varying diameters (arteries, veins, and capillaries)
Eg: Annelids, Cephalochordates and Vertebrates
