64 
THE ACALEPHAE. 
$ 60. 
their body, button and tongue-like organs, which, as they. are connected’ 
with neighboring ganglia, may well be regarded as organs of sense, 
Their essential structure is a membranous capsule, containing a clear 
liquid, in which are suspended crystalline corpuscles. 
These organs, having sometimes a red pigment, have been taken for eyes; 
but, as most of them are without pigment, and as the crystalline corpuscles 
behave in acid like the Otolites of the higher animals, they have more 
recently been better designated as organs of hearing. 
The eight marginal, tongue-like bodies, found upon the dise of Medusa: 
aurita, have been regarded as eyes.” 
The sole fact for the support of this 
opinion is the presence of pigment; for the small hexagonal crystals, irreg- 
ularly scattered in the interior of these bodies, would scarcely allow them 
to refract the light like a crystalline lens. 
The Ctenophora have only a single organ of this nature, and which is 
situated near the ganglion at the posterior end of the body. It has been 
regarded both as an eye and as an organ of hearing. 
With many Discophora, these organs appear as pale-yellow, or even 
eslorless marginal corpuscles, having more or less calcareous bodies. 
It is yet doubtful whether the otolites of the Acalephae perform the same 
movements as those of the acephalous and gasteropod mollusca.® 
1 These marginal corpuscles, already observed in 
the Medusae by Gaede (Beitrage zur Anat. u. 
- Phys. der Medusen, 1816, p. 18, 28), and by Rosen- 
thal (Zeitsch. f. Physiol. Bd. I. Hft. 2, 1825, p. 326), 
were first described as eyes by Ehrenberg. See 
Muiller’s Arch. 1834, p. 571, and Abhandl. d. Berl. 
Akad. 1835, p. 190, Taf. IV. V. 
2 Milne Edwards has called this body, in Lesu- 
euria vitrea and Beroé Forskalit, “ Organe ocu- 
liforme” (Ann. d. Sc. Nat. loc. cit. p. 206, 211, 
Pl. IV. fig. 1, k. and Pl. V. fig. 4, i.). According 
to Will (Froriep’s neue Not. No. 599, p. 67, and 
Hore tergest. p. 45, Taf. I. fig. 2, 4, 20, b.), the red 
pigment of these organs is entirely wanting in 
Beroé, Eucharis and Cydippe, while the hexago- 
nal calcareous corpuscles are very numerous —a 
fact leading him to conclude that these organs are 
auditory vesicles. 
8 According to Wagner (Ueber den Bau, &c., 
and Icon. zoot. Tab. XX XITI, fig. 31, g. 28, c. and 
25), these corpuscles are pale-yellow in Pelagia 
noctiluca, and colorless in Oceania, Cassiopea 
and Aurelia. In Cephea, Will has observed only 
pale-yellow corpuscles, filled with crystals. And, 
according to him (loc. cit. p. 64, 68), the colorless 
pedunculated marginal vesicles of Polyxenia leu- 
costyla contain, each only a single round otolite, 
while those of Cytaeis polystyla contain numbers, 
colorless or yellow, and of irregular forms. He 
has also observed (loc. cit. p. 72, Taf. II. fig 9, 
10) that in Geryonia the number of these otolites 
‘varies from one to nine. Milne Edwards (Ann. 
* [§ 560, note 4.] The organs of sense of the Aca- 
lephae have been the objects of much study of late, 
and to Agassiz we are indebted for the most minute 
researches on these obscure points. He has shown 
the eye-specks to be undoubted organs of sense, 
from their connection with the nervous system. 
With the naked-eyed Medusae, he regards them 
light-perceiving instead of auditory organs. In 
regard to the single organ found with the Cteno- 
phora, and which Frey and Leuckart have re- 
d. Sc. Nat. XVI. p. 196, Pl. I°e.) has observed 
upon the margin of the dise of Aequorea violacea 
vesicles containing two or three spherical corpus- 
cles, and which, probably, are auditory organs. 
According to Sars (Wiegmann’s Arch. 1841, Th. 
1. p. 14, fig. 60), and Wild (loc. cit. p. 75, Taf. IL. 
fig. 21, A. B.), these marginal corpuscles are found 
upon young Medusae belonging to Ephyra. 
4 Will has never observed with the Otolites of 
Acalephae similar movements to those of mollusca. 
Kélliker (Froriep’s neue Not. No. 534, p. 82) has. 
observed vibratile cilia upon the inner surface of 
the marginal corpuscles of Pelagia, Cassiopea, 
Rhizostomum and Oceania, which are pyrifoi 
and contain many calcareous crystals. In the 
pedunculated vesicles of Geryonia, which contain 
only a single crystal, these cilia are absent. In 
none of the Medusae has he found collections of 
pigment, and in Oceania (nov. spec.) only he has 
observed a mass of brown pigment cells upon the 
external and superior surface of the base of these 
corpuscles ; in the centre he perceived a round 
transparent body, and upon the upper surface a 
circular opening, so that the whole closely resem- 
bles an eye, there being, moreover, a kind of pupil- 
lary opening, and the traces of an optic nerve from 
a ganglion. 
According to the observations of Frey and 
Leuckart (Beitr. &c. p. 39), the group of otolites 
contained in the auditory organ of a Cydippe per- 
form oscillatory movements, due evidently to vibrar 
tile cilia situated on the auditive capsule.* 
cently declared to be of an auditory nature, he- 
remarks ; “I am islclined to consider this organ, or- 
this speck, as something similar to the central col- 
ored speck which occurs in the middle of the disc 
in Discoid Medusae, and which is particularly dis- 
tinct in young animals soon after they have been 
detached from the polyp-like stem on which they 
grew, as a remnant of the connection which exista 
between the mother-stem and its progeny, in those 
Medusae which multiply by. alternate genenations.” 
