144 
THE ROTATORIA. $ 184. 
is quite remarkable with, those species whose single or double disc is not. 
crenulate, but entire.” With those whose organs are more numerous, but. 
smaller, this appearance is not observed. 
With Floscularia, and Stephanoceros, the rotatory organs have quite a 
different form. With the first, there are five or six buttdn-like processes. 
about the mouth, covered with very long bristles; these bristles produce 
usually but very feeble motions, and rarely give rise to vortexes. But Ste- 
phanoceros reminds one much of the Bryozoa, for its rotatory apparatus con- 
sists of five tentacle-like processes covered with vibratile cilia® The rota-- 
tory organs differ, moreover, from the ordinary vibratile cilia of epithelium, 
in being under the animal’s control, — that is, moved or kept at rest, at. 
will. 
CHAPTERS III. AND IV. 
NERVOUS SYSTEM AND ORGANS OF SENSE. 
§ 134, 
Notwithstanding the transparency of the Rotatoria, and the distinctness 
with which their organs are separated from each other, yet their nervous. 
system has not yet been made out with certainty, for their bodies are so small 
that their peripheric nerves elude the microscope, and their principal nerves. 
and ganglia cannot be distinguished from the muscular fasciculi, the liga- 
ments, and the contractile parenchyma of the body. 
It appears certain, however, that in all, there is, as a nervous centre, a 
group of cervical ganglia, from which pass off threads in various direc- 
tions. 
1 Conochilus, Philodina, and Actinurus. 
2 Hydatina, Notommata, Synchaeta, and Dig+ 
lena. 
8 See Ehrenberg, Die Infusionsthierchen, Taf. 
XLY. 
4 According to Ehrenberg, there are, at the base 
of each cilium of the rotatory organs, many striated 
muscles, which, acting antagonistically, produce the 
motion (Abhandl. d. Berl. Akad. 1831, p. 34). 
. But neither Dujardin (Infusoires, loc. cit. p. 
579), nor Rymer Jones (Compar. Anat. &c. p. 
120), has been able to perceive this apparatus. 
The contractile parenchyma on which the virbra~- 
tile discs are situated, appears to be destined only 
for the protrusion and retraction of the rotatory 
organs.* 
1 Ehrenberg, to whom we are indebted for our 
uliform body found upon most Rotatoria, and in- 
the neck of Hydatina senta, and Notommata col- 
laris (Abhandl. d. Berl. Akad. 1830, p. 52, Taf. 
VIII. 1833, p. 189, Taf. [X., and, Die Infusionsthier- 
chen, p. 386, &c.). Besides this ganglion, he has 
mentioned with Hydatina, Synchaeta, and Dig- 
Zena, many others scattered through the anterior 
part of the body, and connecting with the cerebral 
one by nervous filaments. Likewise, with Enter-- 
oplea, Hydatina, Notommata, and Diglena, he 
has regarded as a nervous loop, the two filaments 
which pass off from the cerebral ganglion, and go to 
the cervical respiratory orifice. Finally, he refers. 
to the sensitive system, a white sacculus, single'‘or 
double, and situated behind the cerebral ganglion, 
with Notommata, Digiena, and Theorus (Die 
Infusi chen, p. 425). Grant’s description of 
chief information upon the nervous system of these 
animals, first took for a cerebral ganglion the gland- 
* [§ 183, note 4.) Dobie (Ann. of Nat. Hist. 1848) 
speaks of two kinds of cilia with Floscularia ; “‘ one 
of the usual short vibratile kind, covering the inte- 
rior of the alimentary tube; the other extremely 
the nervous system of the Hydatina, as being 
composed of many ganglia and a ventral cord, 
Jong and filiform, of uniform thickness, and not. 
vibratile under ordinary circumstances.” They are: 
slowly moved, being spread out by the contractile 
substance of the lobes of the rotatory organ. — Ep. 
