248 



RITTER 



Test. — Containing many cells of various kinds, but no bladder cells. 

 The granular bodies (cells?) numerous. Calcareous stellate bodies 

 present, though not abundant ; not found at all in some colonies. Rays 

 short and blunt. 



Zooids. — Small, about 2 mm. long ; uniformly distributed. Divi- 

 sion of body into thorax and abdomen distinct ; abdomen considerably 

 larger than thorax, and broader than long. The narrow peduncle con- 

 necting thorax and abdomen always (in specimens at hand) with a 

 deep, narrow constriction at which severance occurs with great ease. 

 Many abdomens free in the test from normal rupture at this point (p1. 

 XXIX, fig. 28). Mantle sending off one or more clfivate ectodermal 

 appendages from the middle region of the body. Longitudinal muscle 

 fibers moderately developed ; a few circular ones also present even in 

 middle portion of thorax. 



Branchial apparatus. — Branchial siphon of moderate length ; six- 

 lobed, the lobes usually distinct though never prominent, sometimes 

 nearly absent. Atrial siphon shorter, though present ; placed far back, 

 and inclined somewhat backward ; lobes as prominent as those of 

 branchial siphon. Branchial sac so much contracted as to make de- 

 termination of internal structure difficult. Tentacles not clearly seen. 

 Three series of rather long stigmata, a considerable area between the 

 peribranchial band and the first series. A delicate muscle band 

 present (?) in the interserial spaces. Endostyle strongly curved from 

 the contraction of the sac, but not tortuous. 



Digestive apparatus. — Loop of intestine very wide, its transverse 

 diameter frequently greater than its longitudinal ; esophagus exceed- 

 ingly narrow, issuing from middle of posterior end of branchial sac. 

 Stomach of liberal size, smooth-walled, nearly globular. Intestine 

 thickest at pyloric end, and gradually tapering to the rectum which 

 seems to terminate at the deep recto-esophageal constriction though 

 found by careful examination to extend to atrium (p1. xxix, fig. 28) . 



Reproductive apparatus. — A single large ovum appears to consti- 

 tute the ovary ; situated on the left-posterior surface of the intestinal 

 loop. The single spherical lobe constituting the testis nearly as large 

 as the ovum, and wholly on left side of the intestinal loop. About 

 four (?) coils to the vas deferens. Embryos not found, though both 

 ova and sperm apparently near maturity. 



This species is very closely related to D. inarviatum v. Drasche 

 {Didemnoides inarmatum Lahille) ; but differs from it in possessing 

 calcareous spicules in the test and in lacking the black pigment patterns 

 characteristic of that species and also in possessing the recto-esophagal 



