Do all animals comprise of a circulatory system?

Circulatory system of animals:

1. A circulatory system is a system that transports nutrients and is involved in the exchange of gases.
2. In vertebrate animals, it comprises a heart, blood vessels, and blood.
3. In invertebrates, the circulatory system is simpler.
4. Many simple animals such as sponges, flatworms, nematodes, and Cnidarians do not possess a circulatory system.
5. Hence, the circulatory system is present in the majority of animals except a few.