Order I. ASCIDIACEA Sessile, with dorsal atriopore (cloacal siphon) ; pharynx with transverse rows of ciliated stigmata, variously shaped, and an internal accessory apparatus of ciliated bars, ridges or papillae.
Section I. Enterogona, Perrier, sens, lat. (= Endoblastica, Garstang)—Gonads unpaired, lodged in the intestinal loop or projecting behind it; budding epicardial; larva with cerebral eye and otolith.
Suborder I. PHLEBOBRANCHIA, Lahille ( =Dictyobranchia, See liger).—Pharynx with accessory, tubular, internal longitudinal vessels, often supporting ciliated papillae ; intestinal loop usually alongside pharynx; budding rare (Perophora, Diazona), the epi cardium in other cases sterile (Ciona) or absent.
Families : Perophoridae, Diazonidae, Cionidae, Phallusiidae ( = Ascidiidae), Corellidae.
Suborder 2. HAPLOBRANCHIA, Lah. emend. Garst. ( = Krikobran chia, Seeliger). Pharynx without ;nternal longitudinal vessels or bars, but with transverse ciliated ridges (horizontal membranes) body elongated, with distinct abdominal region, i.e., intestinal loop always behind the pharynx; budding universal.
Families: Clavelinidae (including Distomidae = Polycitoridae), Gonads in intestinal loop, heart alongside, budding purely epi cardial; Didemnidae, Intestinal loop short, gonads projecting, budding epicardio-intestinal; Polyclinidae (=Synoicidae, Hart), Gonads and heart behind the intestinal loop, budding by post abdominal (rarely abdominal) fission.
Section II. Pleurogona, Perrier ( =Periblastica, Garst.). Gon ads parietal (in atrial wall), usually paired; body compact; budding peribranchial (lateral) larval brain with otolith, but no separate eye ; larval suckers reinforced by a peripheral ring of adhesive papillae.
Suborder 3. STOLIDOBRANCHIA, Lah. ( =Ptychobranchia, See liger). Pharynx with internal longitudinal bars, not tubular ves sels ; its walls often folded longitudinally, or with clusters of bars representing folds ; budding rare (Botryllidae, Polystyelinae); epicardium vestigial or absent.
Families : Botryllidae, Styelidae (=Tethyidae, Hart), Tethyi dae (Huntsman, not Hartmeyer; =Pyuridae, Hart, formerly Cynthiidae), Molgulidae (=Caesiridae, Hart).
Order II. THALIACEA Pelagic, with mouth and atriopore at opposite ends ; pharynx with persistent undivided protostigmata ; budding from a complex ventral stolon, containing both pharyngeal and peribranchial out growths.
Suborder I. PYROSOMATA has the following characteristics: Oozooid incompletely developed. Blastozooids forming a perma nent colony, each hermaphrodite and capable of budding. Proto stigmata numerous, and crossed by internal longitudinal bars. A cerebral eye, and a sub-neural gland, with duct and ciliated funnel, always present. Fam. Pyrosomatidae.—Colony a hollow cylinder closed at one end, the zooids imbedded in its walls, mouths outside, atriopores inside, and endostyles towards the closed end (the starting point). Each zooid has a pair of trans verse lateral muscles connected with fibres in the common test (colonial muscular system). A single egg develops in each cloaca into a ring-like primal colony of 4 zooids (tetrazooid colony). Phosphorescent.
Pyrostremma, nov. gen. (from stremma—a twist or sprain; =Pyrosomata fixata). Protostigmata oblique; a cloacal languet ; "colonial" muscle crossing the pharynx ; also an anterior biradiate muscle-plexus, concentrated dorsally. Stolon multi-annulate, buds not migratory. Orifice of colony guarded by 4 test-processes con taining muscular test-vessels. Two species, P. spinosum, agassizii.
Pyrosoma, s. str. (=Pyrosomata ambulata). Protostigmata at right angles to endostyle. No cloacal languet or anterior muscle plexus. "Colonial" muscle crossing the cloaca. Stolon short ; buds carried to their places by phorocytes. Orifice of colony with sphincter in a test-diaphragm containing vascular processes, e.g., P. atlanticum, verticillatum, etc.
Suborder 2. DOLIOLIDA ( = Cyclomyaria) is characterized by: Oozooid asexual, free-swimming, and budding freely. Peribran chial cavities shallow. Pharynx without internal longitudinal bars. Peripharyngeal bands twisted spirally at their dorsal junction (ciliated spire). Protostigmata in oozooid few (4 pairs), forming a transverse series behind the endostyle, in blastozooids more num erous. Oozooid with a dorsal outgrowth to which the free buds are carried from the ventral stolon by phorocytes. Blastozooids poly morphic, the first being nutritive and sessile ctrophozooids), the second sterile and locomotive (phorozooids), the last sexual (gonozooids). Cloaca posterior, atriopore terminal. Intestine in oozooid uncoiled, with posterior anus. A subneural gland, with duct and ciliated funnel. Eye absent.