§$ 125. 
THE TURBELLARIA. 
CHAPTER V. 
DIGESTIVE APPARATUS. 
§ 125. - 
With the two orders of Turbellaria, this apparatus is formed upon very 
different types. But in both orders, the location of the mouth varies so much, 
that it serves as the basis of genera, according as it is at the anterior extrem- 
ity, or a little behind it, —or, at the middle of the belly, or a little behind 
that also. The walls of the intestinal canal are always intimately blended 
with the parenchyma of the body. ; 
With the Rhabdocoéli, the mouth leads to a muscular cesophagus, which 
is either an annular sphincter, or a longer or shorter tube, but which, in no 
case, can be everted from the mouth. The intestinal canal is a simple cae- 
cum extending from the esophagus to the posterior extremity ; but with 
those species which have the mouth situated more or less posteriorly, it 
stretches forward as a coecum to the anterior portion of the body. With 
the Dendrocoéli the mouth opens into a large throat, containing a protrac- 
tile and very movable deglutitory organ (Pharynz). 
This organ, which can be protruded entirely out of the throat while the 
animal is eating, is either a tube composed of longitudinal and transverse 
muscles, or a collection of lobular and ramified tentacles circularly ar- , 
ranged about the mouth. 
Its base is ‘prolonged into the proper intestine, whose dendritic ramifi- 
cations extend over the whole body. 
Scarcely a trace of salivary or hepatic organs have here been found 
with these animals. ® 
ages on the anterior part of the body of Planaria 
tentaculata, and Eurylepta cornuta, and upon 
the neck of Planocera. With the last, they sup- 
port a part of the eye dots. 
1 The mouth and cylindrical cesophagus of Gy- 
ratrix hermaphroditus, and Vortex truncata, are 
at the cephalic extremity (Ehrenberg, Abhandl. 
d. Berl. Akad. 1835, p. 178, Taf. I. fig. 2,3). But 
the mouth and annular cesophagus of Derosto- 
mum is situated just back of this extremity, into 
which, however, the coecal intestine extends. The 
esophagus is also annular with Mesostomum, 
and T'yphloplana. In the first, the mouth is at the 
middle of the ventral surface ; and in the last, a 
little behind this point, while the intestine projects 
coecally far into the anterior extremity (Orsted, 
loc. cit. Taf. II. fig. 26, 31, and Focke, loc. cit. 
‘Vaf. XVII). 
2 The genus Planaria has become famous for its 
movable organ of deglutition, which, being sepa- 
rated from the body, still continues for a while to 
‘swallow all presented to its mouth (Baer, loc. cit. p. 
* [ § 125, note 2.) With Phagocata (Planaria) 
gracilis, Leidy (Proceed. Acad. Nat. Sc. Phil. IT. 
1848, p. 248) found, instead of a single sucker, 
twenty-three,in the full-grown animal. These are 
all protruded when the animal feeds, but when 
not in use, are closely packed together within the 
animal. They all connect separately with portions 
of the dendritic alimentary cavity. — Ep. 
716, Tab. XXXIIT. fig. 8-11, and Duges, loc. cit. 
XV. p. 152, Pl. IV. fig. 18, 19). 
The large and plicated cesophagus of Planaria 
tremellaris, constitutes the transition to the ten- 
tacular form of the deglutitory organs (Dugés, loc. 
cit. XV. Pl. IV. fig. 20, 21). Fully ramified ten- 
tacles are found with Planocera sargassicola, 
pellucida, and Leptoplana lichenoides. When 
collected in the throat, they present exactly the as- 
pect of aramified intestine (Mertens, loc. cit. Taf. 
I. fig. 2, 3, 6, Taf. IT. fig. 3, 4, and the Isis, 1836, 
Taf. IX. fig. 3, b. 3, c.). The ramified intestine of 
many Dendroco€li has been figured by Baer, Du- 
ges, and Mertens, in their works already cited.* 
3 Focke (loc. cit. p. 196, Taf. XVII. fig. 11, ¢. 
f.) isinclined to regard as salivary and hepatic or- 
gans, two large lateral vessels, and a glandular or- 
gan which he has discovered near the cesophagus 
and intestine of Mesostomum Ehrenbergii ; but 
he himself admits that this view is not yet well 
founded.f 
+ [§ 125, note 3.] Will (Miiller’s Arch. 1848, 
p. 508) has shown that the brownish layer covering 
the whole extent of the intestine of Planaria is 
composed of hepatic glands (Dendrocoélum lac- 
teum, Planaria torva, and nigra), ~- Ep. 
