Hint:It is oval in shape, Amphiblastula larva has a cavity in the middle, the front half of the larva consists of cylindrical, flagellated cells while the other half of the round cells are without flagella.
Let’s discuss the given options and find the correct answer.
The larvae of the Hydra is known as a planula. The cocoon divides into two parts, each of which develops into a male gamete that is released in the water by the other Hydra. The eggs are fertilized externally and the embryo develops to form larvae. The larva attaches to a substratum and develops to form a polyp and then matures into an adult Hydra.
Sycon life history involves amphiblastula larva. Sponges like Scypha are stationary animals. Development in sponges involves a free-swimming larva for dispersal either amphiblastula or parenchyma, development is indirect. A sponge of larva in which the area of flagellate cells is equal to the area of non-flagellate cells.
The reproductive organs begin to develop in early autumn. Cocoons containing fertilized eggs are laid in spring. Fully developed young emerge and develop without metamorphosis but free-living, ciliated larvae are released in a few marine species In most species. In some species, the organism is the complete individual.
The Parenchymula is the larva of sponges. Leucosolenia releases free-swimming hollow larvae called coeloblastula.
Hence the correct answer is option B: Sycon.
Note:The amphiblastula is preceded by a stage called stomoblastula in which the central cavity of a blastula opens outward and is surrounded by round granular cells, micromere.