Aboral surface (opposite to mouth).

Early eight-arm stage.

Stage with three pairs of arms.

Mouth, esophagus, gut and vestibule invagination (larva left side) during six-arm stage. Anal view.

Larva with three pairs of arms.

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

Early with two arms.

Anus in the aboral surface of the juvenile (red structure) and fecal pellets being released.

Lateral view showing the position of micromeres.

Stage with three pairs of arms.

Larva with two pairs of aarms and early development of postero-dorsal arms on the body sides.

Lantern of Aristotle in the oral region.

Non-fenestrated skeleton of antero-lateral arms.

Blastopore and ring of mesenchyme cells secreting the larval skeleton.

Early stage with two arms (post-oral).

Early stage with two arms (post-oral).

Aboral surface.

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

Skeleton and digestive cavity.

Aboral surface.