Aboral surface (opposite to mouth).

Post-oral arm tip in a six-arm pluteus larva.

Early stage with two arms (post-oral).

Polarized light highlights the calcareous skeleton showing the structure of spines, podia, and remnants of the larval skeleton.

Early eight-arm stage.

Lateral view.

Stage with three pairs of arms.

Frontal view of an early two-arm stage pluteus larva.

Stage with four pairs of arms.

Larva with four pairs of arms.

Early stage with two arms (post-oral).

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

Found during an artificial fertilization experiment. We do not know if it is the result of abnormal development or if the larva was reproducing asexually.

Stage with four pairs of arms.

Early stage with two arms, side view.

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

Epithelium.

Primary mesenchymal cells secreting the larval skeleton.

Frontal view of an early two-arm stage pluteus larva.

Larva with four pairs of arms.

Lateral view of mesomeres.

Aboral view.

Early with two arms.