Stage with four pairs of arms.

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

Pre-oral arms.

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.

Post-oral arms and the larval skeleton.

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

Early with two arms.

Stage with three pairs of arms.

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

Aboral surface.

Structure in the anal region.

Arm growing on an unusual site.

Stage with three pairs of arms.

First cleavage

Oral region.

Early eight-arm stage. Oral view showing digestive tract and vestibule invagination next to the left coelom.

Frontal view of the eight-arm pluteus larva.

Zygote.

Intermediate stage between gastrulation and pluteus larva formation.

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

Stage with four pairs of arms.