54 REPORT ON THE TUNIOATA OF PLYMOUTH. 



drical foot-stalk of varying length ; thorax -^ inch in length ; foot- 

 stalk from twice to ten times as long. Abdomen elongate, deeply 

 embedded in the common basal test. 



Colour. — A band of golden-yellow pigment extends along the 

 ventral side of the thorax and is continued into the oesophageal 

 region ; it is absent from the dorsal side ; this band gives a 

 conspicuous colouration to the zooids, when seen alive with the 

 naked eye. 



Test of a pale green colour, semi-transparent ; thin around the 

 thorax, thicker and firm in the oesophageal region, cartilaginous in 

 the basilar mass ; traversed by stolonial tubes in the basal, abdo- 

 minal, and even oesophageal regions ; in the latter region (that of 

 the foot-stalk) the tubes are generally sterile. 



Apertures circular, proximate, in the median sagittal plane ; 

 branchial terminal, cloacal subterminal. 



Branchial sac with seven to nine rows of stigmata ; horizontal 

 membranes well developed, broad ; dorsal languettes borne on the 

 horizontal membranes, long and stout ; endostyle of great size ; 

 aperture of hypoganglionic gland simple, circular. 



Cardiac structures (pericardium, epicardium) as in Glavelina ; 

 pericardium not recurved. 



Habits. — Irregularly attached along with masses of Polyzoa 

 {Bugula, Scrwpocellaria, &c.), calcareous sponges [Leucosolenia] , 2i,\idi 

 compound Ascidians {Botryllus, Didemiium) to varied objects from 

 rough ground in 10 — 20 fathoms water (e. g. cases of tubicolous 

 Annelids, Gorgonia stems, shelly debris) ; rarely forming a thin 

 carpet on the stems of red weeds, such as Delesseria. 



I first noticed this beautiful little Tunicate in the winter and early 

 spring of 1889, when it was dredged several times on rough ground 

 off the Mewstone, on one occasion to the west of it, but generally 

 from half to two miles south or south-west of the rock. This is cer- 

 tainly the best locality for the species at Plymouth, although curiously 

 enough the first specimen was dredged on January 26th in shallower 

 water inside the Breakwater, north-west of the chequered buoy. This 

 first colony was attached to the stem of a Delesseria, and formed a 

 thin crust over its surface, the zooids having very short stalks (see 

 PI. II, fig. 3) ; the colony was unusually free from adventitious 

 foreign bodies, and the configuration of its parts, especially of the 

 basal test, was much more obvious than in specimens dredged off 

 the Mewstone. These latter colonies are almost inextricably bound 

 up with Polyzoa, Botryllids, Sponges, and other organisms, forming 

 tangled masses in which usually only the brightly gleaming heads 

 of the zooids are visible, the basal test being hidden beneath 

 numerous other organisms and foreign bodies. It is a very 



