Final answer:
The larval forms in jellyfish eggs belong to animals in the subphylum Cnidaria, class Scyphozoa, and are known as planulae, which settle and develop into polyps before maturing into adult jellyfish.
Step-by-step explanation:
The larval forms found in jellyfish eggs belong to the animal in the subphylum Cnidaria, which undergoes a complex life cycle involving various stages of development. In the class Scyphozoa, for instance, the larvae of these marine jellies are known as planulae. After fertilization, a planula larva is formed, which later settles on a substratum and develops into a sessile polyp. This polyp can reproduce asexually or may start to produce medusa buds, eventually giving rise to the adult jellyfish form.
Additional larval forms are seen in other aquatic species. For example, in crustaceans, larval stages such as nauplius or zoea are prevalent, and in the case of barnacles, a cypris larva is typical during early development. Meanwhile, most mollusks produce a trochophore larva that may be followed by a veliger larva before the final metamorphosis to the adult form.
In conclusion, the larval form found in each of the six jellyfish eggs can be identified as a planula, characteristic of the subphylum Cnidaria, specifically falling within the class Scyphozoa. These jellyfish display a distinct life cycle that is valuable for understanding the reproductive and developmental patterns of marine invertebrates.