1917] Eitter-Forsijth : Ascidians of Soutlicnt California 479 



Zooids. — Numerous, distinctly seen through test, arranged in very 

 regular systems, on au average about a dozen individuals in a system, 

 occasionally as many as twenty, in a system. The three regions of 

 body, thorax, abdomen, and postabdomen. distinctly set off from one 

 another, making it difficult to extract zooids entire ; never much con- 

 tracted ; little pigment matter in tissue ; musculature very feeble ; 

 mantle thin and transparent ; entire structure easily made out by 

 examining animals in situ in slices of colony. Length of zooids about 

 4.5 mm. ; length of branchial sac about 3 mm. ; postabdomen slightly 

 longer than abdomen ; musculature very weak. About sixteen delicate 

 longitudinal muscle bundles extending from branchial siphon back- 

 ward to terminate about midway the length of branchial sac ; a few 

 delicate encircling fibers in branchial siphon; stronger fibers constitut- 

 ing a sphincter muscle around atrial orifice. 



Branchial system. — Branchial orifices easily seen on surface of 

 colony; each with six broad scallops when fully expanded, but becom- 

 ing pointed lobes upon contraction. Atrial orifice overarched by a 

 long broad languet often truncated but sometimes with three delicate 

 terminal lobes; size and shape of languet depending upon age of 

 zooid and its position in system. Tentacles eighteen to twenty-six, of 

 three lengths, the six longest nearly as long as the half-diameter of 

 circle in which they are situated. Number of series of stigmata from 

 thirteen to seventeen ; about thirteen or fourteen very regular stigmata 

 in each half -series; number of series as well as number of stigmata 

 increasing with age of zooid; a small muscle band in each inter- 

 stigmatic vessel ; papillae on interstigmatic vessels regular in size and 

 arrangement, there being one for the interval between every two 

 stigmata. Dorsal languets very regular, one for each interstigmatic 

 vessel. Endostyle narrow and straight. Atrium exceptionally large 

 and well-defined. 



Digestive ■system (pi. 46, fig. 71). — Small in proportion to size of 

 branchial sac ; lateral flexure of intestinal loop pronounced, the antero- 

 posterior axis of stomach being brought nearly to a right angle with 

 the long axis of branchial sac. Esophagus emerges from dorsal pos- 

 terior angle of branchial sac and bends abruptly ventrally to a right 

 angle to enter the smooth-walled stomach which is slightly asynuuet- 

 rical and a little longer than broad. Intestine usually divided into 

 three portions; fir.st, the part immediately behind stomach which is a 

 little longer than stomach and has a bulge about midway of its length ; 

 next, a connecting piece that lies on left side and enters enlarged 

 rectal limb by a very .small, short, cylindrical tubule; and third, the 

 long rectal piece having two blunt caeca on each side of proximal end. 

 Rectum runs first parallel with stomach, then passes to left of eso- 

 phagus and ends in a constricted aims a little less than half way up 

 branchial sac. 



Postabdomen elongated, pear-.shaped, connected with abdomen by 

 a narrow peduncle near intestinal loop; containing but little mes- 

 enehymatous tissue, and a large and distinct heart (/(., pi. 46, fig. 71) 

 situated in its posterior end. 



Reproductive si/stem (o. and t.. fig. 71). — Not voluminous, situated 

 in postabdomen about midway of its length, compact, the testicular 

 lobes (t.) and ovary (o.) closely intermixed; vas deferens (r.d.) con- 



