What is the major difference between an open circulatory system and a closed circulatory system? see section 33.1 (page 621) ?

An open circulatory system is when blood and oxygen do not run through veins, an example would be a crab or earthworm. A closed circulatory system is when blood and oxygen flow through veins, humans and dogs being an example.

I don't know if this is the answer you're looking for, but an open system is defined as a "system in exchange of matter with its environment, presenting import and export, building-up and breaking-down of its material components." Closed systems, on the other hand, are held to be isolated from their environment.