TUNICATA OP THE PRIBILOF ISLANDS. 



619 



It- 



colony. (Fig. 14, area B, exaggerates the distinctness of the branchial orifices.) The 

 common cloacal appertares wholly obliterated to superficial inspection. Branchial 

 siphon found, after isolation of zooids, to be six lobed. Atrial siphon with a broad' 

 languet the distal edge of which is armed with three small processes (fig. 16). 

 Branchial tentacles about 24 in number, rather large, though a few small ; not forming 

 a well-defined single circle. Eather close to the branchial orifice. Branchial sac well 

 developed. About 15 series of stigmata and about 16 stig- 

 mata in each half series; these very regular in form and size. 

 The interserial vessels broad and each containing a well-devel- 

 oped muscle band. (Fig. 15, m. e. v.) 



Dorsal languets long and slender, about one for each series 

 of stigmata. 



Digestive tract, — CEsophagus (fig. 15 ce) issuing posterio- 

 dorsally from the branchial sac, longer than the stomach; 

 deflected to the right side by the rectum. Stomach spherical, 

 smooth walled both without and within. Duodenal portion of 

 the intestine with two well-marked constrictions. Eectaf por- 

 tion large and straight, runs far forward, nearly in the median 

 dorsal line, which it reaches by a left curvature of the duo- 

 denal portion. (Fig. 15.) 



Sexual organs. — Gonads contained in the large pear-shaped 



pedunculated postabdomen; ovary a well-defined mass, confined 

 to the enlarged posterior portion of the postabdomen. (Fig. 

 16, ov.) 



The ova pass into the atrial chamber, where they take a 

 position in its posterior portion and to the right side. The 

 larvae are developed in this incubatory chamber. No male 

 gonads have been found in any of the specimens examined. 

 No buds have been seen ; and as the colonies at hand are all 

 in a state of prolific sexual reproduction, it seems probable that 

 in this species there is an alternation of periods of sexual and 

 asexual reproduction. 

 This species seems to be more closely related to PolycUnum fungosum Herdman, 

 1886, than to any other known member of the genus, but it is distinctly different 

 from this in the following points: (1) In P. fungosum the "colony 

 has a plano-convex discoid form." " The lower surface is almost 

 flat, and the point of attachment is at the center." (2) The 

 branchial sac has 10 or 12 rows of stigmata in P. fungosum and 

 15 in P. globosum, and the stigmata appear to be longer and less 

 numerous in the rows in the former than in the latter species. 

 The collection contains but a single colony of this species. \ j^J /7B. 



Polyolinum pannosum, new specieB. 



General character of colony. — Form variable, from quite regu- 

 larly pear-shaped to depressed and irregularly elliptical. Not distinctly peduncu- 

 lated, though some colonies show a tendency in this direction. Largest colony in 

 collection measures 3 cm. 



