§ 61. 
THE ACALEPHAE. 65 
CHAPTER V. 
DIGESTIVE APPARATUS. 
§ 61. 
The digestive apparatus of the Acalephae is formed after several very 
different types. The mouth is sometimes single and central, or there may 
be many of them. It is often surrounded with arms and retractile filaments, 
which are endowed with the prehensile and nettling organs just described. 
The digestive cavity, which is always lined with ciliated epithelium, has. 
distinct walls, which are united immediately to the parenchyma of the 
body, leaving, therefore, no surrounding cavity. 
With those having a single mouth the stomach is of a variable size, and 
has often caecal appendages. With Beroe,“ the mouth is very large and 
free from tentacles, and opens into a very spacious stomach which occu- 
pies nearly the whole body. But with Cestum, Cydippe and Lesueuria, 
the stomach is small, and appears like a cavity in the body; and with 
Cytaeis, Thaumantias and Geryonia, it is likewise small, and has the 
shape of a tubular projection.” 
That of Medusa has four saccular folds,” that of Pelagia® six, and that 
of Cyanea thirty-two. 
When the mouths are numerous, either, as in the Rhizostomidee,” there 
are many canals which conduct the food through the arms upon which the 
mouths are situated into the central stomach; or, as in the Siphonophora, 
each mouth opens into a particular tubular stomach. With these last, 
however, a certain number of their tentacles are hollow, and have a mouth 
at the extremity. As it has been observed that these suck in food and 
digest it, their orifices have been regarded as mouths, and their cavities as 
stomachs, 
1 Milne Edwards, Ann.d.Sc. Nat. XVI. pp. 5, 6. 
2 Eschscholtz, loc. cit. Taf. I. II.; and Milne 
Edwards, loc. cit. Pl. III. 
8 Will, loc. cit. Taf. IT. 
4 Baer, in Meckel’s deutschs. Arch. VIII. 1823, 
Taf IV. fig. 2; also, Ehrenberg in Abhandl. a. 
Berl. Absa 1836, Taf. III. fig. 1. 
5 Wagner, Icon, zoot. Tab. SXXII1. fig. 5. 
6 Gaede, loc. cit. Taf. IL. 
7 Eysenkardt, Nov. Act. physico-med. X. part 
II. p. 391, Tab. XXXIV. fig. 1 (Rhizostomum 
Cuviert). 
8 This is so, for examples, in Diphyes (Will, loc. 
cit. Taf. II. fig. 22); in Physalia (Olfers Abhandl. 
d. Berl. Akad. 1831, p. 162, nat I.) 3 in Stephano- 
mia (Milne Edwards, ‘Ann. d. Sc. Nat. XVI. Pl. 
VIL. IX. X.); and in Physophora (Philippi, 
Miller’s “Arch. 1843, Taf. V. fig. 1 1, 4). 
(Loe. cit. p. 316.) On a preceding page he says: 
“That this may be the case seems probable when 
we consider the relation of the two sorts of appa- 
ratus in the two types. The upper nervous ring in 
Sarsia bears the same relation to the central ali- 
mentary cavity, and to the pigmented disc, that the 
ganglion and eye-speck of Beroe bear to the chy- 
6* 
Philippi, however, affirms that in this last 
genus these canals are organs of absorption, and that 
the true stomach, which has a simple mouth, is 
concealed at the base of the tentacles (loc. cit. Pp. 
63, Taf. V. fig. 10). 
I think, however, that this opening belongs to the 
respiratory system, as also does a.similar opening 
in Veledia and Porpita, which Lesson (Voyage de 
Dupertey 106 cit. p. 49, 56, No. 6, fig. B. ; and No. 
7, fig. C. C.) has regarded ‘as a mouth, 
The tentacles of these animals are noth- 
ing but stomachs ; and Lesson himself has called 
them “poches stomacales,” since they digest 
food. It would, moreover, be strange that these 
organs, which, in P: , have been to. 
be stomachs, should perform another function in 
Physophora, Veleila, and Porpita, where their 
structure is the same. But further researches are 
miferous system, which opens above its gelatinous 
disc, notwith ding these openings.” (p. 248.) 
This point, fully as interesting from its zoological 
importance as from its morphological relations, 
can be settled only by a knowledge of the embryol- 
ogy of these animals. — Ep. 
