TUNICATA OF THE PRIBILOF ISLANDS. 



521 



Digestive tract. — (Esophagus rather wide at its mouth, issuing from uearly the mid- 

 dle of the posterior end of the branchial sac, distinctly curved so as to enter the stomach 

 on its right dorsal side. Stomach globular, smooth walled. Intestinal loop rather 

 wide, slightly shorter than the combined length of oesophagus and stomach. Two well- 

 marked constrictions in the intestine at the base of the loop, these including between 

 them the base of the U-shaped loop; the rectum passing to the left of the oesophagus 

 to reach the atrial chamber. Anus sometimes with a wide, flaring lip. (Fig. 18.) 



Sexual organs. — Ovary not large, situated far back in the post-abdomen, behind 

 the testis. The entire post abdomen so filled with mesenchymatous cells that the 

 sexual organs are much obscured; no distinct lobulation of either ovary or testes 

 observable. The embryos, developing in the atrial chamber, greatly distend and dis- 

 tort this cavity. 



This species appears to be more closely related to P. aurantiiim, Milne-Edwards, 

 than to any other member of the genus. The last-named species is, however, described 

 by both Milne-Edwards, 1842, and LahilJe, 1890, as having a gelatinous test, and no 

 mention is made by either of these authors of the network of fibers in the test. This 

 latter character, I take it, constitutes a distinct difference between the two. The 

 presence of such a network seems to be of such 

 rare occurrence in Polyclinum that were it pres- 

 ent in P. auranthmi, Lahille, whose studies were 

 largely morphological, would have noted it. 

 Furthermore, according to the figure of a zooid 

 of P. aurautium, given by Milne-Edwards (PI. 

 Ill, fig. 4, b), the postabdomen of this species is 

 relatively much longer than in 1\ pannosum. 



There are about two dozen colonies of this 

 species in the collection, all from St. Paul Island. 



Aplidiopsis jordani, now species. 



Ueneral character of the colony. — Massive, ■.d.s. 



irregularly i)olyhedral iu form, the three dimen- B 



sions not greatly different. Attached by a small 



area only (fig. 19). Quite hard and unyielding to the touch; surface rather uneven. 

 Light gray in color, with the yellowish zooids distinctly visible. A thin surface 

 layer of test considerably harder and less transparent than the interior ijortions, 

 which latter is quite transi)arent. A few sand grains imbedded on the surface. 



Greatest diameter of the one colony in the collection, 2.3 cm.; least diameter, 

 1.5 mm. 



Cells iu test very numerous, rather uniform iu size. No vessels present in the test. 



Zooids. — Eather large and numerous, readily seen on the surface of the colony. 

 No systems present, each zooid opening to the surface by its own atrial orifice. Many 

 of the individuals placed at very oblique but differing angles to the surface of the 

 colony, so that they are crossed by and wound around one another. Post-abdomen 

 not pedunculated. A finger-like ectodermal process projecting from posterior end of 

 body. Total length about 8 mm., one-fourth of which is branchial sac, another fourth 

 intestinal loop, and the other hnlf post abdomen. (The post-abdomen outlined in fig. 

 20 is unusually short.) Post-abdomen very large at its posterior end, and is dense and 



