54 PHYLUM TUNIC AT A (UROCHORDA). 



Blumenbach, very like Salpa, Th. democratica-mucronata Forsk. Pegea 

 Sav., very like Salpa but with supposed traces of stigmata (hemitremata) 

 on its dorsal wall. lasis Sav., like Salpa, but with several embryos at 

 different stages of development in the same sexual animal. 



The abyssal form Octacnemus Moseley, discovered by the Challenger 

 Expedition and described by Moseley* is placed here ; why, it is difficult to 

 see, for it does not appear to possess any important salp-like feature. 

 Octacnemtis bythius Moseley, body octoradiate, medusa-like, flattened 

 antoro-posteriorly, probably attached, test gelatinous, thin, transparent ; 

 pharynx with no stigmata or openings into the atrial cavity ; digestive 

 organs coiled up to form with the reproductive organs a nucleus which is 

 placed posteriorly ; S. Pacific. Our knowledge of its structure is limited, 

 and nothing is known about its budding and reproduction. 



A second imperfectly known colonial speciesf O. patagoniensis Metcalfe 

 from 1,000 fms. off the coast of Patagonia has been assigned to this genus. 



Sub-order 2. Cyclomyaria (Doliolida). 



Barrel-shaped Thaliacea with thin test, and pharynx with two 

 rows of stigmata on its posterior wall. The asexual form has a 

 ventral stolon which buds and produces three kinds of zooids, one 

 of which develops sexual organs. The muscular rings are complete 

 ventrally and a tailed larva is always developed. 



Doliolum is a transparent pelagic organism with a thin test in 

 which there are no protoplasmic elements and no cellulose. The 

 pharynx (Fig. 46) occupies the anterior part of the body and the 

 atrial cavity the posterior, the digestive canal and the heart (5) 

 together with, in the sexual form, the gonads being aggregated 

 together in an inconspicuous nucleus behind the pharynx on the 

 ventral side of the atrial cavity into which they project. The 

 mouth (1) and atrial (17) openings are at opposite ends of the 

 body and terminal, and the edges of both are lobed. There are 

 no tentacles The dorsal tubercle (22) is surrounded by the 

 spirally coiled, dorsal ends of the peripharyngeal bands, and the 

 pharynx, which has an endostyle (3) but no dorsal lamina, 

 possesses only two rows of stigmata placed in its posterior wall 

 (20). There is a ganglion and closely adjacent subneural gland 

 (21), which opens in front of the peripharyngeal band by the 

 dorsal tubercle (22). The muscular bands of the body-wall are 

 in the form of complete hoops, of which there are nine in the 



* Trans. Linn. Soc. (2), 1, p. 287, 1876. See also Herdman Challenger 

 Reports, Tunicata, Pt. Ill, 1888. 



t Metcalfe, Johns Hopkins Univ. Circ., 12, 1893, Fig. 8. 



