In cnidarians, the mouth of both the medusa and polyp form opens into an internal where digestion takes place.

The correct terms to fill in the blanks are gastric cavity and extracellular. In cnidarians, the mouth of both the medusa and polyp form opens into an internal gastric cavity where extracellular digestion takes place. The polyp and medusa are body forms that can be found in the phylum Cnidaria. The polyp is a nonmotile body form while the medusa is a free swimming body form.

Amight be the answer

When you are making a guess you are forming a hypothesis