$$ 59, 60. THE ACALEPHAE. 63 
CHAPTER III. 
NERVOUS SYSTEM. 
§ 59. 
A nervous system has been found in many Acalephae. With the Cteno- 
phora the cesophagus is surrounded by a ring formed of eight ganglia,” 
and at the opposite extremity of the body there is a simple ganglion. Five 
nervous filaments pass out from these ganglia, and along the sides of the 
body are nervous fibres, which ultimately divide into delicate threads, 
The tentacles of Medusae are supplied with nervous filaments which issue 
from a ganglion situated at their base.® 
CHAPTER IV. 
ORGANS OF SENSE. 
§ 60. 
With many Acalephae, there are, 
1These eight ganglia, which are connected 
together by delicate cords, were first observed by 
Grant (Trans. Zool. Soc. Lond. I. p. 10) in Cydip- 
pe pileus. Compare, also, Wagner, Icon. zoot. 
Tab. XXXIII. fig. 37, A. B. From each of these 
ganglia two nerves pass off to the side, while a 
third, traversing the interior of the body, and hav- 
.ing two or three swellings, is finally distributed to 
ithe intestine. Patterson (The Edin. new Philos. 
Jour. XX. p. 26), and Forbes (Ann. of Nat. Hist. 
1839, p. 145), have also observed the oesophageal 
wing in Cydippe, but did not perceive the ganglia. 
2 Milne Edwards (Ann. des Sc. Nat. loc. cit. 
p- 206, Pl. IV. fig. 1) has observed at the poste- 
rior extremity of the body of Lesueuria vitrea 
a new Beroid) a ganglionic body which sends 
* | § 59, note 3.) The nervous system of the 
-Acalephae has been successfully studied by 4gassiz 
upon several genera (Hippocrene, Tiaropsis, 
Staurophora). His results are new, and different 
from those of previous observers. J cannot do bet- 
ter than to quote his words: “There is, unques- 
tionably, a nervous system in Medusae, but this 
nervous system does not form large central masses, 
to which all the activity of the body is referred, or 
from*which it emanates. There is no regular com- 
munication by nervous threads between the centre 
and periphery and all intervening parts; and the 
nervous substance does not consist of heterogene- 
ous elements, of nervous globules and nervous 
threads, presenting the various states of complica- 
tion and combination, and the internal structural 
differences, which we notice in the vertebrated ani- 
anals, or even in the Mollusca and Articulata.” 
upon the borders and extremities of 
out in front four filaments ; and upon the sides of 
this animal a nervous cord, from which pass off 
delicate branches at regular intervals. At the pos- 
terior extremity of the body of Cydippe, Eucha- 
rig and Medea, Will (Froriep’s neue Notizen, 
No. 599, 1843, p.’67, and Hore tergest. p. 44) has 
likewise observed a round, yellowish ganglion, with 
four prolongations, from which pass off twenty-five 
or thirty nerves. 
3 Ehrenberg has found along the entire border 
of the disc of Medusa aurita, and between each 
two tactile filaments, a bifid nervous ganglion. He 
affirms to have seen also two others similar, at the 
base of each tentacle surrounding the genital organs. 
See Abhandl. d. Berl. Akad. 1835, p. 203, Taf. IV. 
fig. 1, x.; and Mudler’s Arch. 1834, p. 571.* 
“In Medusae the nervous system consists of a 
simple cord, of a string of ovate cells, forming & 
ring around the lower margin of the animal (Pl. V. 
fig. 11, 2, 4, 5), extending from one eye-speck to 
the other, following the circular chymiferous tube, 
and also its vertical branches, round the upper 
portion of which they form another circle. The 
substance of this nervous system, however, is 
throughout cellular, and strictly so, and the cells 
are ovate. There is no appearance in any of its 
parts of true fibres” (loc. cit. p. 232). That 
this is the nervous system seems placed beyond all 
controversy ; for, in a private letter, Agassiz has 
informed me that in a new genus (Rhacostoma), 
living on the shores of Massachusetts, he has seen 
this system at night as an illuminated diagram. — 
Ep. 
