During the polygastric phase of Amphicaryon acaule, there are two nectophores of differing sizes and shapes. No reserve buds are present. The larger larval nectophores are retained, while the younger heteromorph nectophores are vestigial and shield-like. The ostium is positioned slightly below the nectophore’s surface. The somatocyst is small, distinct, and curved. The hydroecium is large, circular, and shallow, located on the upper lateral side of the nectophore. Each eudoxid has either a male or female gonophore, with the female gonophore carrying four ova.