While collecting specimens, a marine biologist finds a sessile Cnidarian. The medusas that bud from it swim by contracting a ring of muscle in their bells. To which class does this specimen belong?

a. Class Hydrozoa

b. Class Cubozoa

c. Class Scyphozoa

d. Class Anthozoa

Phylum Animals that display radial or biradial symmetry and are diploblastic, or develop from two embryonic layers, ectoderm and endoderm, are included in the phylum Cnidaria. About 99 per cent of cnidarian species are marine-based.

Nerve cells are arranged in scyphozoans into a nerve net that covers the entire body and a nerve ring that surrounds the edge of the bell. Rhopalia, or groups of sensory organs, may be found in the bell's edge pockets. The dome of the jelly's body is lined with a ring of muscles that provides the contractile force needed to swim through water and draw in food as they swim.

• The medusoid type of Hydrozoa is known as a hydromedusa because it possesses a muscular veil or velum below the bell's border. The medusoid form of Scyphozoa, which lacks a velum, is known as a scyphomedusa.
• The cubozoans have muscular pedalia, which have one or more tentacles attached to them, at the corners of the square bell canopy.
• Multiple chambers are separated within the Anthozoa's cavity by longitudinal septa referred to as mesenteries. Each mesentery is made up of a layer of mesoglea sandwiched between sheets of gastrodermis tissue in a fold.