The primary difference between a coelom and a pseudocoelom is .

The coelom is covered by mesoderm layer but the pseudocoelomate are not covered

Explanation:

The multicellular organism is made of three layers: the ectoderm, endoderm and mesoderm. The organism which possesses the true cavity is known as the coelomates and their coelom is covered by the mesoderm.

The organisms which do not possess the true cavity but cavity-like structure are called pseudocoelomates and their coelom is known as the false or pseudocoelom. The pseudocoelomates are not fully covered by the mesodermal layer.

Thus, The coelom is covered by mesoderm layer but the pseudocoelomate are not covered