j2 PHYSIOLOGICAL SERIES. 



D 7 Two specimens of the nervous system of an Earthworm 

 (Lwnbrifu* terrtttri*) showing the anterior part isolated and 



>le system I'M >>". 

 The cerebral ganglion is small and bilobed. It is situated 



above the p<> '"' fthe I'""'" 1 L>avit y in the third 



body-wgmt-iit. and is unii.-d by a \ . air of fibrous connectives 

 to tin- ventral cord. 



Tin- latter lies free in the body-cavity, and swells slightly 

 within each segment to form a ganglion, from which three 

 pair* of nerves are given off to the body-walls. Between 

 th,- ganglia, tin- cord is almost, though not quite, free from 



S.T. 



c!n. 



B.L 



through a Ventral-chain Ganglion of Lumbricus 

 terrain*. X 126. 



r. I Illood-VMwI. C.M. Central medulla. G.C. Ganglion - cells. 

 mnt fibre*. M. Muscle-fibres. NL 1 , NL a . The two 

 Uyer of neorilemma. S.T. Supporting tissue. 



ganglion-crll.H. Tin- mitral nervous system is surroumlrd 

 by a netirilcmma, in whu-h two layer- arc difltinguishable : 

 (i.) an outer layer largely composed of longitudinal inux-lc- 

 fibir, (ii.) an inner cuticular layer. Within the cuticle 

 lie the connectives and ganglia emlKMldiul in a supporting 

 fibrous tisane (? neuroglia) (fig. 8). Three medullated giant 

 fibres run along the dorsal surface of the cord ; their 

 relations to the rest of the system are still obscure, but it is 

 certain that at the him In i-nd of the cord the two lateral 



