[ 485 ] 



XXVII I. On the N'ervous Si/stem of Molluscous Anhncds. By Robert Garner, 



Esq., F.L.S. 



Read November 4th, and December 16th, 1834. 



1 HOUGH in this paper the author originally included the nervous system 

 of the Rudiata, yet he now, upon more mature consideration, determines to 

 confine his observations to Molluscous animals, convinced that he can add 

 little of importance to the recent labours of the German anatomists* in this 

 department, who have shown the errors of their predecessors, and themselves 

 discovered the true nervous system of Radiated animals. 



In the Tunicnta the nervous system consists of a ganglion and nerves 

 (Tab. XXIV. fig. 1. A, cr, h.), generally very visible on slitting the cartilaginous 

 covering. In Phallusla intestinalis, Sav., we discover this single, yellowish 

 ganglion, lying upon the muscular coat between its two orifices. In other 

 species we see the ganglion nearly divided. One set («.) of filaments surround 

 the branchial orifice, and give nerves to its tentacula, and appear to meet on 

 the opposite side, forming in the Phallusia a nerve which seems to run along 

 the edge of the elongated branchial fold. The other set {h.) supply the mus- 

 cular tunic, and also the mantle, and go towards the mouth. In Cynthia, 

 and those Tunlcata, which have thick muscular tunics, the ganglion is not 

 visible external to the muscular sac, it being situated in its interior. The 

 above-described ganglion is, according to Cuvier, analogous to the posterior 

 or branchial ganglion of Conchifera. In the figure are shown two minute 

 bodies (G.) seen on the intestine of Phallusia, which Meckel suspects may be 

 ganglia, but which as probably may be traces of a second ovary. 



* More particularly Tiedemann and Ehrenberg. Spix appears to have been mistaken in his ac- 

 count of the ganglia and nerves of the Actinia, as he certainly was in that of the nervous system of 

 the Asteritts. The author's observations agree vnth. those of Leuchart, Rapp, and Meckel in this respect. 

 The nerves of Radiata are exceedingly minute and difficult to discover ; in preparations the vessels are 

 often shown for them. 



