NEET BIOLOGY

Detailed explanation-1: -The medusa is a free-swimming form; it moves by rhythmic muscular contractions of the bell, providing a slow propulsive action against the water. The other principal body type of the adult cnidarian is the polyp, a stalked, sessile (attached) form. Compare polyp.

Detailed explanation-2: -Cnidarians have two basic body forms, medusa and polyp. Medusae, such as adult jellyfish, are free-swimming or floating. They usually have umbrella-shaped bodies and tetramerous (four-part) symmetry.

Detailed explanation-3: -Corals and sea anemones are polyps. Most of these animals are small, but a few sea anemones can grow as large as 1 meter in diameter. The second structural form that cnidarians have is called the medusa form. Medusa bodies are shaped like an umbrella with the mouth and tentacles hanging down in the water.

Detailed explanation-4: -planula, plural planulae, free-swimming or crawling larval type common in many species of the phylum Cnidaria (e.g., jellyfish, corals, and sea anemones). The planula body is more or less cylindrical or egg-shaped and bears numerous cilia (tiny hairlike projections), which are used for locomotion.

Detailed explanation-5: -So, the correct answer is the polyp is cylindrical and fixed, medusa is umbrella-like and free swimming.