Biology · Kingdom Animalia

Balanoglossus is a genus of ocean-dwelling acorn worms (Enteropneusta). Many hemichordates such as acorn worms have a larval stage in their life cycle; the larvae, called tornariae, swim using microscopic hairs called cilia. The tornaria larva resembles the bipinnaria larva of echinoderms.

Bipannaria is a bilaterally symmetrical free-swimming larva characteristic of echinoderms that swims using ciliated bands.

Radiolarians are protozoa of the class Polycystinea, found in the upper layers of all oceans. Radiolarians, which are mostly spherically symmetrical, are known for their complex and beautifully sculptured, though minute, skeletons, referred to as tests.

Balanoglossus is a genus of ocean-dwelling acorn worms (Enteropneusta). Many hemichordates such as acorn worms have a larval stage in their life cycle; the larvae, called tornariae, swim using microscopic hairs called cilia. The tornaria larva resembles the bipinnaria larva of echinoderms.

Trochophore is a small, translucent, free-swimming larva characteristic of marine annelids. Trochophores are spherical or pear-shaped and are girdled by a ring of cilia (minute hairlike structures), the prototroch, that enables them to swim.