446 



ZOOLOGY 



situated in the bases of the parapodia. A delicate longitudinal 

 neural vessel accompanies the nerve-cord. 



Nereis is devoid of any hrniwhuv ; but there can be little doubt 

 that the lobes of the parapods with their rich blood-supply, and the 

 areas of integument occupied by plexuses of blood-vessels, subserve 

 the function of respiration. 



There is a well-developed nervous system (Fig. 352), which is 

 bilateral and metameric in its arrangement, like the other systems 



Fin. 3.^2. — rfereis. — Anterior portion o£ nervous system, comprising the brain, the cesopha 

 and the anterior part of the ventral nerve-cord. (After Quatrefages.) 



connec 



01 organs. Situated in the prostomium is a large bilobed mass 

 of nerve-matter containing numerous nerve-cells, the cerelral 

 ganglion or hntin (f). This gives oS tentacular nerves to the tentacles 

 and palpi, and two pairs of short thick optic nerves to the eyes. 

 Behind, two thick nerve-strands, the ce^ophageal connectives {d), curve 

 round the mo\ith in the peristomium to meet on the ventral 

 aspect behind the mouth and below the pharynx. The oesopha- 

 geal connectives with the cerebral ganglion thus form a ring 

 around the anterior part of the enteric canal. From them are 



