Nocturnal- describes animals that are active primarily at night for example earthworms.
Coelom- the body cavity, which contains visceral organs.
Bilateral Symmetry- a condition in which there are two equivalent sides form and arrangement of parts.
Psuedocoelm- a fluid filled body cavity partly lined with the mesoderm.
Exoskeleton- hard cover on the outside of the body that provides the structure for the animal.
Endoskeleton- internal body structure.