Post-oral arm.

Ossicles of the lantern of Aristotle in formation at the oral region.

Larva with six arms.

Stage with three pairs of arms.

Post-oral arms and the larval skeleton.

Oral region with the lantern of Aristotle in formation.

Oral region with the lantern of Aristotle in formation.

Early with two arms.

Larva with three pairs of arms.

Stage with four pairs of arms.

Digestive tube and coeloms during growth of the antero-lateral arms.

Larva with three pairs of arms.

Larva with six arms.

Growth of antero-lateral pair of arms (2nd pair).

Ambulacral feet and spines.

Lateral view. Detail of the lantern of Aristotle under the peristomial membrane (where mouth will open).

Oral region with the lantern of Aristotle in formation.

Oral region with the lantern of Aristotle in formation.