Pyrosoma Spinosum, Herd/man 223 



languets, which marks the point of attachment to the dorsal stolon in 

 young zooids, and the dorsal nucleus. In other species of Pyrosoma 

 the languets and the dorsal nucleus are closely approximated. The 

 number of languets is about twelve, of the usual form. The endostyle 

 is bent at an angle of about 140 degrees at its anterior third. The 

 stomach and gut are of a greenish-brown colour, the oesophagus being 

 bright red. They lie in the horizontal plane, the gut being folded 

 back laterally along the left side of the stomach. 



The ovary was only observed in a few zooids. It contained a 

 single ovum ; a testis was not found in any instance. The presence of 

 filaments running through the test, and putting into communication 

 the atrial muscles of separate zooids, has been noted by several 

 observers (Huxley, 1860 ; Seeliger, etc.). Similar fibres could be 

 seen in P. spinosum, and numerous acicular and fusiform cells, similar 

 to those composing the filaments, were evident, scattered irregularly 

 through the test and, much more densely, in the body-walls of the 

 zooids themselves. 



It will be seen from the above remarks that P. spinosum differs 

 very markedly from all other members of the genus. The principal 

 differences may be summed up as follows : 



Test processes situated ventral to the oral openings of the zooids. 



Atriopore with the sphincter incomplete. 



Anterior position of the atrial muscle. 



Wide separation of dorsal ganglion and dorsal languets. 



List of Authorities quoted. 



Farran (1906), ' On the Distribution of the Thaliacea and Pyrosoma in Irish 

 Waters, 1 'Fisheries, Ireland, Sci. Invest., 1 1906, 1. [1906]. 



Herdman (1888), 'Report on the Tunicata, 1 Pt. iii. ; Challenger Reports, Zool., 

 vol. xxvii. 



Huxley (I860), ' On the Anatomy and Development of Pyrosoma, 1 Trans. Linn. 

 Soc, vol. xxiii., 1860. 



Perrier (1886), ' Les Explorations Sous-marins 1 {Talisman Expedition). 



Seeliger (1895), ' Die Pyrosomen der Plankton Expedition,' Bd. ii., E. b. 



