= | 
wh. 
TUNICATES. 695 
attached to the lower surface of the nerve-mass and containing 
calcareous bodies would seem to represent the auditory capsule and 
its otolithes!.] Such an organ also, but containing a concrement of 
a more composite form, was discovered by Escuricut, similarly 
situated in a simple Ascidian Chelyosoma Macleayanum, and noted 
as the auditory organ? in 1841. 
The muscular system in Ascidie consists of a layer of fibres, 
which cross each other on the inner covering of the body (the so- 
called mantle), but run principally in a longitudinal direction. In 
the Salpe muscular bands are seen remote from each other, which, 
like a girdle not entirely closed at one part, surround the internal 
cavity of the body, the respiratory space. These bands consist of 
fibres that run parallel to each other in the direction of the bands, 
and thus form a right angle with the longitudinal axis of the body. 
On the position of these animals in the natural system there 
can exist no doubt when they are referred to the common type of 
the molluscs. They must be regarded as the lowest division of 
these animals, that immediately close in upon the bivalves. The 
compound Ascidians in propagating by gems remind us of lower 
animals of the class of the Polyps. More especially still do the 
Ascidians resemble the Bryozoa (comp. I. pp. 92,93), but we should 
prefer to unite these last with the Mollusca, rather than on account 
of this affinity to separate the Tunicata from the Mollusca. 
Species of this class are met with in all seas. The Salpe are 
numerous in the Mediterranean and in the ocean, especially between 
30° and 40° N. and §. Lat., in colder regions and in higher latitudes 
they are of more rare occurrence although they extend to 50° N. 
and §. Lat., and were once observed near the Norwegian coast even 
lina. V. BENEDEN in a species of Ascidia named by him Ascidia vitrea, found eight eyes 
at both openings; Rech. s.l. Ascid. simples, p.61, Pl. tv. fig. 2. In Ascid. ampulloides 
V. Bern. such eye-points cannot be seen, but when young and still moving freely the 
animal has one or two black eye-points ; ibid. p. 40. 
1 [Hoxuey 1. 1. p. 571, Pl. xvi. fig. 2.] 
2 Escuricut Anatomisk Beskrivelske af Chelyosoma Macleayanum of SOWERBY, 
Kjébenhayn, 1841, quoted by Sresotp Vergl. Anat. 1. p. 260 (note), who suspects 
from the figures of DELLE Cu1aJE and Savieny that the organ exists very generally in 
this class. Minne Epwarps (see the figures of Salpa referred to above in the illus- 
trated edition of Cuvipr) thinks that it must be regarded as an organ of vision. 
That Mryen had observed this organ lying above the central nerve-mass, I collect 
from his figure, Tab. xxvut. fig. 18. 
