694 GLASS XI. 
The nervous system presents a single ganglion, which in the 
Ascidie is placed on the internal covering of the body, usually 
regarded as the mantle, between the two tubes into which the body 
is elongated. Besides other nerves which radiate from this ganglion, 
there appears to arise from it a nervous ring that surrounds the 
tube by which the water penetrates (the oral and respiratory tube). 
Other ganglia which are noticed in Ascidians by some writers, are at 
the least to be regarded as doubtful. In Salpa a ganglion (or a 
nerve-mass formed of several ganglia united) lies close behind the 
anterior, broader opening on that surface of the body which is directed 
upwards?, Several nerves run radiately from this nerve-mass. 
Vestiges of organs of sense are not entirely absent. In the 
Ascidie at the branchial aperture a circlet of small filiform feelers, 
sometimes digitally incised or pennated, is found. In the Salpee 
there lies in front of the central mass of the nervous system an 
organ of an elongated form, consisting of two lamine with an 
internal margin smooth and an external striated, which Escuricut 
regards as an organ of feeling and compares with the four lamelle 
which surround the mouth in bivalve molluscs’. Organs of sight 
also have been observed in the Ascédie. There are found both 
around the branchial aperture of the mantle and around the aper- 
ture towards which the extremity of the intestinal canal proceeds, 
a ring of eye-points, often of a yellow colour‘. [In Salpe a vesicle 
1 Thus ScHALK, whose Dissert. de Ascidiarum Structura I am acquainted with 
from citations alone, records a nerve-ganglion in the posterior part of the body, 
between the convolutions of the intestine ; GRANT speaks even of three ganglia, Out- 
lines of Comp. Anat. 1811, pp. 205, 206. Compare on the nervous system of the 
Ascidie, Cuvier Sur les A scidies, p. 15, Pl. 11. fig. 2, o, fig. 5, g. Saviany Mém. 2, 
pp. 117, 118, Pl. x. fig. 2, 1 D, &e. 
2 This position of the central portion of the nervous system caused EscHRICHT to 
give to the surface the name of ventral side. See on the nervous system of Salpa 
MeyYEN 1.1. s. 395, and the fig., Escuricut Anat. physiol. Undersigelse over Salperne. 
Kjobenhayn, 1840, 4t0, printed from the Vidensk. Selsk. Naturvid. og math. Skr. VII. 
pp- 12—14, Tab. 1, fig. 3u, Tab. 1. fig. 8 upfig. 12; Minne Epwarps in Cuvier R. 
Ani., éd. ill., Mollusg. Pl. 120, fig. 1 b, a, Pl. 121, fig. 2 a, h, fig. 2 b. 
3 [HuxuEy Anat. of Salpa and Pyrosoma, Ph. Trans. 1851, p. 871, calls this 
“‘léngliches organ” of Escuricat “‘languet.” He supposes that it may subserve the 
gustatory function. It floats freely in the respiratory cavity to which it is attached by 
its base. | 
4 Grant Outlines, p. 361, says that in Ascidia (Phallusia) intestinalis eight red 
eye-points lie round the branchial opening, and six around the efferent tube ; so also, 
according to the investigations of WILL in various species of Cynthia Sav. and Clave- 
