Phylum which is bilaterally symmetric segmented animal with tough, chitinous exoskeleton.
Phylum contains crustaceans, insects, spiders, centipedes and millipedes.
Composed of the heart, blood vessels, lymphatic vessels, lymph, and the blood. Primarily marine invertebrates, but also includes land snails and slugs. Peristalsis serves to push material contained within the organ along its length.