( 181 ) 

 ORIGINAL COMMUNICATIONS. 



Further Observations on the Structure of Appendicular^ 

 Flabellum (Chamisso). By T. H. Huxley, F.R.S. 



(Plate X.) 



In a paper read before the Royal Society in 1851, I gave an 

 account of a very singular animal which had been frequently 

 observed and described under various names, as Appendicu- 

 laria (Chamisso), Oikopleura (Mertens), Fritillaria (Quoy and 

 Gaimard), Vexillaria (J. Miiller), and Eurycercus (Busch), 

 but whose precise place in the animal kingdom was still a 

 matter of doubt. The essential points in that account will be 

 found in the following extracts : — * 



* * * * 



" The animal has an ovoid or flask-like body one-sixth to one-fourth of 

 an inch in length, to which is attached a long curved lanceolate appendage 

 or tail, by whose powerful vibratory motions it is rapidlyjoropelled through 

 the water. " 



" The smaller extremity of the animal is perforated by a wide aperture 

 (d) which leads into a cliamber, which occupies the greater part of the 

 body, and at the bottom of this chamber is the mouth. The chamber 

 answers to the respiratory cavity of the Tunicata, and is lined by an inner 

 tunic distinct from the outer ; the space between these, as in the Salpce, 

 being occupied by the sinus system. 



" On the side to which the caudal appendage is attached, an endostylc 

 (c), altogether similar to that of the Salpw, lies between the inner and 

 outer tunics ; and opposite to this, or on the ventral side, close to the 

 respiratory aperture, there is a nervous ganglion, to which is attached a 

 very distinct spherical auditory sac, containing a single, also spherical, 

 otolithe. The sac is about l-200th of an inch in diameter. The otolithe 

 about l-800th, figs. 1, 2, 4 a. 



'* Anteriorly, a nerve is given off from the ganglion («) which becomes 

 lost about the parietes of the respiratory aperture ; another large trunk 

 passes backwards (b) over the left side of the oesophagus, and between the 

 lobes of the stomach, until it reaches the appendage, along the axis of 

 which it runs, giving off filaments in its course, fig. 2." 



" There is no proper branchia ; but that organ seems to be represented 

 by a richly-ciliated band or fold (c) of the inner tunic, which extends from 

 the opening of the mouth forwards, along the ventral surface of the 

 respiratory cavity, to nearly as far as the ganglion ; when it divides into 

 two branches, one of which passes up on each side, so as to encircle the 

 cavity (/). This circlet evidently represents the ' ciliated band ' of 

 Salpa. 



•' The mouth ((/)is wide, and situated at the posterior part of the ventral 

 parietes of the respiratory chamber. The oesophagus (A) short, and slightly 

 curved, opens into a wide stomach ( J) curved transversely, so as to present 

 two lobes ix)steriorly. 



* Nova Acta Acad. Curiosorum, t. xi. pars secunda, pp. 313 and 314. 

 VOL. IV. O 



