$$ 135, 136. 
THE ROTATORIA. 145 
§ 135. 
Beside the sense of touch, apparently located chiefly in the rotatory 
organs and their tentaculiform processes,” these animals have also an 
organ of vision. Usually this consists of a single or double eye-speck 
upon the neck; and sometimes, though rarely, of three or four red specks 
upon the forehead. These specks are usually very small, but nicely defined, 
and covered by a kind of cornea, They are situated immediately upon the 
cerebral ganglion, or are directly connected with it, by nervous filaments. 
CHAPTER V. 
DIGESTIVE APPARATUS. 
§ 136. 
The digestive apparatus is well developed with the Rotatoria, and has 
the following parts: 
The mouth opens into a muscular pharynx which has two horny, masti- 
catory organs, which move laterally upon each other. 
Succeeding this 
pharynx is a narrow oesophagus of variable length, which leads to a stomachal 
(Outlines, &c., p. 88, fig. 82, B.), is founded, un- 
dly, upon supposition, and not upon real ob- 
servation.* 
1 The vibratile disc of Conochilus has upon its 
centre, four cylindrical processes, terminating usu- 
ally by a bristle, and quite resembling antennae. 
The two or four styles projecting from the front of 
Synchaeta, are probably of the same nature. 
2 The eye-speck is simple with Euchlanis, No- 
tommata, Synchaeta, Cycloglena, and Brachio- 
nus ; double with Conochilus, Megalotrocha, 
Diglena, Rotifer, and Philodina ; with Eosphora, 
there are three, and with Sguamedia, four ; while 
Hydatina, Enteroplea, Ptygura, Tubicolaria, 
and the adult Flosculariae, have none at all. 
8 Ehrenberg, who was the first to regard these 
red dots as eyes, has given their intimate structure 
in none of his writings; this is the more to be 
*[§ 134, note 1.] Gosse (Ann. Nat. Hist. 1850, p. 
21) describes the nervous system of Asplanchna 
priodonta as follows : ‘ Each of the three eyes rests 
-n a mass that appears ganglionic; the clubbed 
masses at the lateral apertures are probably of the 
same character ; and the interior of the body con- 
tains a number of very delicate threads, floating 
freely in the contained fluid, which have thickened 
knobs here and there, especially where they anas- 
tomose.”” 
Leydig (Zur Anat. und Entwickelungsgeschichte 
der Lacinularia socialis, in Siebold and Kélliker’s 
Zeitsch. Feb’y, 1852, p. 457) describes a very pecu 
liar nervous system with Lacinudaria, consisting 
of: “1, A ganglion behind the pharynx, composed 
13 
regretted since Dujardin has not regarded them 
as visual organs (Infusoires, p. 591). He sup- 
ports this view by the fact that they disappear with 
the adult individual ; but this objection will appear 
valueless when it is remembered that this is also 
true of certain parasitic Crustacea. At all events, 
the small ocular dots of Conochilus, Rotifer, and 
Philodina, are nicely-defined organs surrounded 
with a solid capsule, and appear to me wholly dif- 
ferent from the diffused masses of red pigment 
which Ehrenberg has erroneously taken for eyes 
with the Infusoria. The disproportionate size of 
the red dots which Ehrenberg (Die Infusionsthier- 
.chen, Taf. LI, LIT. LVI.) has figured with Notom- 
mata forcipata, Synchaeta baltica, Cycloglena, 
and Kosphora, lead one to suppose that they are: 
only collections of pigmentary granules. 
of four bipolar cells with their processes. 2. A gan~ 
glion at the beginning of the caudal prolongation, 
similarly composed of four Jarger ganglionic cells 
and their processes.” But, that these parts belong 
to the nervous system, appears by no means posi- 
tive ; for, as, this observer candidly observes, and 
it is, I think, a capital comment on this whole 
class of study: ‘‘ That these cells, with their radiat- 
ing processes, are ganglion globules and nerves, is 
w conclusion drawn simply from the histologicat 
constitution of the parts, and from the impossibility 
of making anything else out of them, unless in- 
deed, organs are to be named according to our 
mere will and pleasure.” — Ep. 
