284 



POLYGORDIUS 



LESS. 



(Fig. 69, I\/v. F.) interspersed with nerve-cells {Nv. C). In 

 the cord the fibres are arranged longitudinally, and the 

 nerve-cells are ventral in position, forming a layer in imnie- 



JJrr Eptbm 



Fig. 69. — Diagram illustrating the relations of the nervous system of 

 Polygordius. 



The deric epithelium (^Der. Epthni) is either in direct contact with the 

 central nervous system (lower part of figure), or is connected by afiferent 

 nerves (a/, nv) with the inter-muscular plexus {int. muse, plx) : the 

 latter is connected with the muscle-plates {M. Pt) by efferent nerves 

 {Ef. nv). 



The central nervous system consists of nerve-fibres {Nv. F) and 

 nerve-cells {Nv. C) : other nerve cells {Nv. C) occur at intervals in 

 the inter-muscular plexus. 



The muscle-plates {Af. Pf), one of which is entire, while only the 

 middle part of the other is shown, are invested by a delicate protoplasmic 

 network, containing nuclei (««), to which the efferent nerves can be 

 traced. (The details copied from Fraipont. ) 



diate contact with the deric epithelium. In the posterior 

 lobe of the brain the nerve-cells are superficial and the 

 central part of the organ is formed of a finely punctate 



