Larval stage tailed, with elongate envelope and intermediate vesicle between tail and cephalo-enteron. Old nurse large, up to 12 mm long; M3, M4, M5, and M6 wider than the rest, M4 and M5 predominant. Gastrozooids with main axis up to 1 mm long, with few gill-slits (less than 12), digestive tract U-shaped, anus located more ventrally than the entrance of the esophagus, fixation peduncle slender, without expansions. In both phorozooids and gonozooids, endostyle running from M23/4 to M42/3. Neural ganglion at M31/4. Gill-septum slightly arched, extending dorsally and ventrally to M5, its posterior bend extending to M51/2. With 10 to 14 pairs of gill-slits. Ovary before M6. Testis pear-shaped, bulging ventrally between M5 and M6. Gonozooids up to 4 mm long; the gonozooids of the variety krohni Borgert, 1894 are bigger, up to 7 mm long (endostyle from M2 to M43/4, gill-septum strongly arched, its posterior bend surpassing M6, with 40 to 45 pairs of gill-slits).