Open circulatory system

From Freepedia

An open circulatory system is an arrangement of internal transport in which blood bathes the organs directly and there is no distinction between blood and interstitial fluid.

Grasshoppers have this kind of circulatory system; the blood is pumped from the tail to the head, and then is released into the body cavity, where it makes its way to the tail again. Because the grasshopper's blood doesn't carry oxygen, it doesn't need to circulate as quickly. Spiders also have this type of circulatory system.