Notes on the morphology of the Tunicata. 573 



would indicate that possibly the animals were attached to some solid 

 object. It is as possible, however, that the animals normally live 

 upon the mud bottom and that the entanglement of solid particles in 

 the fine processes from the test of some individuals was accidental. 

 The individuals are not solitary, but are attached to one another in 

 a linear series by means of a slender stolon (Fig. 81). 



A median section reveals most of the internal anatomy. The 

 mouth connects with a large pharynx underlying the oral disc (Fig. 81 C 

 ph). Most of the remainder of the body is occupied by the huge 

 atrium (cl) which is separated from the pharynx by a delicate, imper- 

 forate, horizontal septum. The atrium communicates with the exterior 

 l)y means of the atrial aperture already described. 



The viscera are gathered into a compact mass which lies in the 

 atrium, suspended from the middle of the horizontal septum. In this 

 mass are found the "oesophagus", stomach and intestine, the ovary 

 and the testis, and the whole is covered by a delicate membrane 

 evidently the lining of the atrium (Fig. 81 C, cf. also Fig. 87, a drawing 

 of the visceral mass of 0. hithyus). On the back of the visceral mass 

 are a number of peculiarly arranged muscles (cf. Fig. 81 B and Fig. 84). 

 Below these muscles, not far from the oesophageal aperture lie the 

 brain and the neural gland with the ciliated funnel (Fig, 86, cf. also 

 Figs. 82 and 87, drawings of 0. hithyus) as described in Section I 

 of this paper, page 549. The ciliated funnel opens into the ''oeso- 

 phagus" not far behind the point where the latter opens into the 

 pharynx. On the side of the visceral mass opposite to the muscles, 

 are a pair of oval perforations which extend through the investing 

 membrane and into the "oesophagus" (Figs. 81 B and C and 

 85). The visceral mass sends out two cords of tissue from its lower 

 end, which pass into the stolon that unites the individuals into a linear 

 colony (Fig. 81). These two cords are formed partly from the in- 

 vesting membrane of the visceral mass and in part from the wall of 

 the stomach. I am unable to say whether the endoderm or only the 

 connective tissue of the stomach wall enters into them. 



Looking a little more in detail at the different organs, we find, 

 first as to the alimentary canal (Fig. 81 C), that the pharynx has 

 been much modified, the chamber assuming a peculiar shape and the 

 stigmata being wholly lost. Herdman and Moselet find the stigmata 

 in 0. hithyus represented by numerous imperforate pits in the mem- 

 brane separating pharynx from cloaca. In 0. patagoniensis I cannot 

 find even these. The pharynx opens below by a circular aperture 



