Gemmules are infrequent and appear in clusters of varying sizes, featuring openings directed towards the substrate. Gemmoscleres are plentiful and form a protective capsule around each gemmule, but they are not embedded in the gemmule pneumatic layer. The individual gemmules are sizable, possessing a thick coat with a diameter ranging from 603 to 809 micrometers (SDI6 = 63), and they have a simple foramen. The gemmoscleres are smooth amphioxea, resembling miniature megascleres. In S. aspinosa, the thick-coated gemmules are organized into small groups, and their openings face the substrate.