Chap, xii.] NERVOUS SYSTEM OF CCELENTERATA. 395 



sense hair, which, acted on by movements in the 

 water, and communicating with the body of the cell, 

 is able to bring the animal into relation with the 

 outer world. 



In the sea-anemones the basal processes of the cells 

 have been observed to be continued into a layer of 



Fig. 167. Part of the submuscular pleius of Amelia aurita, showing 

 ganglionic cells. (After Schiifer.) 



fibres, which are, to all appearance, nervous in nature. 

 Well-developed ganglionic cells are to be found 

 scattered in the layer of nervous fibres which sur- 

 rounds the mouth. 



While in Aurelia and other Acraspedote Me- 

 dusae the central part of the nervous system consists 

 of isolated ganglia, ordinarily eight in number, the 

 Craspedote Medusse, or those in which the edge 

 of the bell is provided with a velum, have a more 

 definite central system; the epithelial coverings of 



