Larval stage with a spherical envelope and a rudimentary tail. In young oozooids, alimentary canal extending horizontally in the sagittal plane, endostyle extending from M2 or M3 to M5, stomach in front of M6. Gastrozooid with main axis up to 4 mm long, with 10 to 40 gill-slits, alimentary canal U-shaped, anus situated dorsally to the entrance of the esophagus (or at the same level in younger forms), fixation peduncle with 2 distal tunical expansions. In both phorozooids and gonozooids, endostyle extending from M21/3 to M41/2, neural ganglion at M31/4, gill-septum extending dorsally to approach M3 and ventrally to M5, its posterior bend extending to M53/4-M6. Ovary near M7. Testis opening near the ovary and running forward dorsally to about M2 or beyond. Gonozooids up to 12 mm long.