304 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



ducing no impairment of any of the functions of 

 the pedicels, spines, or peflicellari?e), and then to 

 paint with strong acid the inside of the shell — com- 

 pletely washing out the acid after about a quarter 

 of a minute's exposure. The results of a number 

 of experiments conducted on this method may be 

 thus epitomized : — 



The effect of painting the back or inside of the 

 shell with strong acid {e.g. pure HCl) is that of at 

 first strongly stimulating the spines into bristling- 

 movements, and soon afterwards reducing them to 

 a state of quiescence, in which they lie more or less 

 tiat, and in a peculiarly confused manner that 

 closely resembles the appearance of corn wdien 

 " laid " by the wind. The spines have now entirely 

 lost both their spontaneity and their power of 

 responding to a stimulus applied on the external 

 surface of the shell — i.e. their local reflex excita- 

 bility, or powder of closing in upon a source of irri- 

 tation. These effects may be produced over the 

 whole external surface of the shell, by painting 

 the whole of the internal surface ; but if any part 

 of the internal surface be left unpainted, the cor- 

 i-esponding part of the external surface remains 

 uninjured. Conversely, if all the internal surface 

 be left unpainted except in certain lines or patches, 

 it will only be corresponding lines and patches on 

 the external surface that suffer injury. It makes 

 no difference wdiether these lines or patches be 

 painted in the course of the ambulacral feet, or 

 anywhere in the inter-ambulacral spaces. 



The above remarks, which have reference to the 



