250 



RITTER 



regular, not contracted away from the upper surface of the colony ; 

 the three divisions of the body, as seen in their natural position in 

 the colony conspicuously set off from one another, the post-abdomen 

 by its light reddish yellow color and by its abrupt constriction from 

 the abdomen, the abdomen by its pale dirty green and by its shoitness 

 and thickness, and the thorax by its ashy color and prominent endo- 

 style. As a rule the thorax -and abdomen combined seem to con- 

 stitute nearly one-half the length of the entire body, as seen with the 

 zooids in place in the colony; in reality, however, the post-abdomen 

 is considerably longer than these two together (p1. xxx, fig. 30). 



Test. — Not great in quantity, because the zooids are so closely 

 crowded ; no bladder cells or vessels present ; cells small, numerous, 

 often containing pigment, particularly in surface layers. 



Mantle. — Very delicate ; longitudinal muscle fibers arranged in a 

 few definite bands ; circular muscles almost wholly wanting. 



Branchial apparatus. — The six lobes of the branchial siphon 

 sometimes short and broad, sometimes rather long and slender ; con- 

 stant in number. Atrial siphon short; its languet usually long and 

 pointed, frequently trifid. Branchial tentacles counted with difficulty ; 

 about ten or twelve in number, of unequal sizes, situated very near the 

 branchial siphon. Branchial sac about 3 mm. long and 2 mm. deep. 

 Usually ten (rarely nine or eleven) series of stigmata ; in one zooid 

 (immature?), only seven; the individual orifices long and narrow and 

 very regular. About eighteen or twenty stigmata in each half series. 

 The interserial vessels narrow ; a rather delicate muscle band in each. 



Digestive tract. — Intestinal loop short (never as long as the bran- 

 chial sac) and wide. Esophagus very short, in preserved specimens 

 usually hardly recognizable; loop of the intestine behind the stomach 

 also very short. Distal portion of the ascending limb of the intestine 

 lying at the left side of the stomach and esophagus, rather than dorsal 

 to them, thence turning almost with a right angle to reach, in its rec- 

 tal portion, the left dorsal aspect of the branchial sac. The form of 

 the intestinal loop thus approximates the twisted condition of this 

 organ as found in Polyclinum (p1. xxx, fig. 30). 



Stomach large and prominent, nearly globular, but generally some- 

 what broader than long, its position slightly transverse to the general 

 long axis of the animal. Folds in the wall numerous (twenty or more) , 

 many of them very regular and extending without interruption the 

 entire length of the organ. In some cases, they are broken up into 

 islands, some elongated, others nearly round ; in others the folds branch 

 and anastomose with one onother. On the dorsal-sinistral side a nar- 



