314 PHYSIOLOGY OF THE INVERTEBRATA. 



cellarige ; and from tlie surface of the shell to the capsular 

 muscles at the bases of the spines (Mg. 59). 



Fig. s8.— External Nerve-plexus of Echinus. 

 {^After Romanes and Ewart.) 



" In the case of the pedicellarise, the plexus on reaching 

 the stem runs along between the calcareous axis and the 



Fig. 59.— Nekve-cells lying among Muscular Fibres at the 

 Base of a Spine in Echinus. 



{After Romanes and Ewart.) 



surface epithelium, to reach and extend over and between the 

 muscular and connective tissue-fibres between the calcareous 



