314 



PHYSIOLOGY OF THE INVERTEBRATA. 



cellariro ; and from the surface of the shell to the capsular 

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



Fig. 58. — ExTERNAi. Nerve-plexus of Echinus. 

 (A//C/- Romanes and Ewart.) 



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

 the stem runs along between the calcareous axis and the 



=2^ 



Fig. 59.— Nkkvk-celi.s lying among Muscular Fibres at the 

 Base ok a Simne in Echinus. 



iAftcr Romanes and Ewakt.) 



surface epithelium, to reach and extend over and between the 

 muscular and connective tissue-fibres between the calcareous 



