SEA-NETTLES. 105 



giving off three nerves, of which the largest ran lengthwise between 

 two bands of cilia 1 close to the external surface of the body; but a 

 later observer, F. WILL, was not so fortunate as to find this system 

 of nerves. On the contrary he detected a conical ganglion above 

 the funnel-shaped structure from whence the water-canals arise, 

 consequently opposite to the mouth. From this ganglion many 

 fine threads arise, to be distributed to the substance of the body 

 and its different parts. In the same situation MILNE EDWARDS also 

 saw a ganglion in the genus Lesueuria, from which numerous 

 nerves, collected into four bundles, arose 2 . 



EHRENBERG considers the eight prominent organs, situated in 

 Medusas, at the edge of the disc, to be eyes : they contain a sandy 

 or stony concrement, a quantity of minute hexagonal prismatic 

 crystals composed of carbonate of lime. Such calcareous concre- 

 ments are often found in the animal organism in the neighbourhood 

 of nerves ; as for instance in Frogs by the sides of the vertebral 

 column near the exit of the spinal nerves. A red pigment which 

 moreover generally distinguishes these marginal corpuscles, (it is 

 sometimes wanting,) caused EHRENBERG to conjecture that they 

 were eyes 3 . There is more probability in KOELLIKER'S idea, that 

 they are to be considered as auditory organs 4 . Even in vertebrates 

 little stones or grit of carbonate of lime are found in the auditory 

 sac or vestibule of the membranous Labyrinth. In Beroe and the 

 allied genera only a single organ of the sort is found, a pedunculated 

 vesicle with calcareous crystals at that end of the body which is 

 opposite to the mouth 5 . 



The apparatus for motion consists of transparent muscular 

 fibres, having sometimes a longitudinal, sometimes a circular 

 course : they exhibit the same microscopic transverse stripes which 

 are characteristic of the voluntary muscles of higher creatures 6 . 



Several of the Animals belonging to this Class are phospho- 

 rescent. According to EHRENBERG the Arabians on the Red Sea 



1 Trans. oftkeZooloy. Soc. London,!. 1833, P- IO - 



2 Ann. des sc. not. IQ Srie, Tom. xvi. Zoolog. p. 206. 



3 Die AkalepJicn, s. 14. 



4 FRORIEP'S Neue Notizen, xxv. Bd. (Januar. 1843) s - 8l 8 4- 



5 MILNE EDWARDS, 1. 1., WILL, Horce Tcrgest. s. 45, 46. 



6 WAGNER Ban der Pelagia noctiluca ; his Tab. Zoot. xxxm. fig. 30 ; WILL, 1. 1. 

 s. 4649- 



