RINGED-WORMS. 2A 
Nereide QUATREFAGES fand this system to be composed of differ- 
ent ganglia, and named it, on account of its position on the pro- 
boscis, systéme susesophagien, or proboscidien supérieur. 
With respect to organs of sense, with the exception of tentacles 
and other appendages subservient to a finer sense of touch, for sight 
there are found in most species only coloured spots, usually black, 
of variable number, as special organs. According to I. MuELLER’s 
investigations in a Nereis, the eyes of ringed-worms contain no 
transparent parts, but are merely swellings of the visual nerves sur- 
rounded by black pigment. ‘They are endowed with sensibility for 
light, and the worms can distinguish between light and darkness: 
but what is properly named sight, perception of the form of objects, 
such eyes cannot afford. In Alctopa lepidota KRroun however found 
a lens and a vitreous body. A special auditory organ has not been 
detected ; the first portion of the cesophagus is supposed to be the 
seat of taste. 
The organs of motion are in some more complicated than in 
others. In all muscular fibres are found beneath the skin, which 
may be separated more or less completely into layers: the external 
layer has a circular, the internal a longitudinal course. In some, as 
Aphrodite, these fibres are united to form distinct bundles. By means 
of the layers or bundles the body can be moved, contracted, extended, 
bent. Besides this general muscular system, motion of the body 
in the Leech can be also effected by means of a suctorial dise at its 
posterior part, in which there are circular and radiating fibres. The 
proboscis, which is capable of eversion and retraction, has proper 
muscles for these purposes. Concerning the bristles and hairs, 
which are found on many, we have already spoken above. These 
parts, springing from the sides, supply fixed points for the motions 
of the body, like the spines of the Echind: they are retracted, ex- 
tended or moved sideways by proper muscles. 
Many species of this class diffuse a phosphoric light. It is 
1 There lies also a small ganglion in front of the brain (ganglion cervical QuaTRE- 
FAGES), and from the lateral parts of the brain a thread arises, which with that of the 
other side surrounds the mouth (Systéme sous-esophagien labial au proboscidien 
infériewr); this last portion of the nervous system may be compared with the arrange- 
ment in the Mollusca gasteropoda. See on the nervous system of the Annelids 
a memoir of QUATREFAGES illustrated with beautiful figures, Ann. des Sc. nat. 3¢ Série, 
Tom. 11. Zoologic, 1844, pp. 81—r1o04. 
