30 PHYLUM TUNIC ATA (UROCHOKDA). 



sand, rarely pedunculated, pharynx with 4 or less than 4 folds on 

 each side, gonads in the form of a number of small separate masses 

 scattered over the inner surface of the mantle, calcareous spicules in 

 connective tissue of the mantle, most seas. 



Fam. 3. Molgulidae. Usually free, sometimes fixed, rarely 

 stalked ; test usually covered with sand adherent to long, hair-like 

 processes of the test (Fig. 21) ; mouth 6-lobed, atrial aperture 4-lobed ; 

 dorsal tubercle extremely variable, being circular, slightly spiral, and 

 largely spiral within the limits of a single genus ; pharynx wall usually 

 longitudinally folded* (57 folds on each side), internal longitudinal 

 bars without papillae, stigmata more or less curved, usually arranged 

 in spirals (Fig. 22) ; tentacles usually much branched, of two or three 

 regularly alternated sizes ; intestine attached to inner surface of 

 mantle on left side ; renal organs aggregated in a sac upon the right 

 side ; gonads on inner surface of mantle, usually paired (Fig. 22) ; 

 larvae anurous in a few species. 



Molgula Forbes (Fig. 19), apertures not laciniated, pharynx with 

 6 or 7 folds, most seas. Anurella L.-Duthiers, very similar, larvae 

 anurous. Gymnocystis Giard. Pera Stimpson, pharynx with 5 folds, 

 Atlantic and Arctic. Ascopera Herd., stigmata not in spirals, lobes 

 of the apertures plain, abyssal, test without processes, stalked, Ker- 

 guelen. Ctenicella L.-Duthiers, apertures laciniated, Med. Eugyra 

 Alder and Hancock, pharynx not folded, but with saccular diverti- 

 cula in longitudinal rows, gonads unpaired, most seas. Paramolgula 

 Traustedt, pharynx without folds, stigmata spirally coiled and in in- 

 fundibula, gonads paired. Bostrichobranchus Traustedt ; Gamaster 

 Pizon. Oligotrema Bourne, New Britain. 



Tribe 2. ASOIDIAE GOMPOSITAE (SYNASCIDIA) | 



Fixed (except Coelocormus) colonial forms, the individuals of 

 which reproduce by gemmation and are embedded in a common 

 test (except Clavelinidae}. 



The embryos usually undergo their development in the atrial 

 cavity or in a special incubatory pouch which they do not leave 

 until they have developed into the tailed larva. 



Fam. 1. Botryllidae. Colony usually thin and encrusting, sometimes 

 in the form of thick fleshy masses ; zooids arranged in systems (Fig. 23) 

 circular or elliptical or in branching lines, the zooids of a system opening 

 into one common cloaca ; common cloacal openings distinct, usually lobed : 

 zooids short, not divided into regions, disposed almost tangentially to the 

 surface of the colony ; intestine on th,e left side of the posterior part of 



* The folds are really longitudinal rows of saccular projections (infundi - 

 bula) of the pharyngeal wall into the peribranchial cavity. 



j- Pizon, Histoire^de la blastogenese chez les Botryllides, Ann. Sci. Nat. 

 (7), 14, 1893. Id., Embryogenie de la larve double des Diplosomides, 

 Compt. Rend., 1893. Id., Etudes biologiques sur les Tuniciers Coloniaux 

 fixes, Bull. Soc. Quest France, 10, 1900. Hjort, Ueb. d. Entwickelungs- 

 cyclus der zusammengesetzten Ascidien, Naples Mit. 10, 1893, p. 584. 



