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



movements are interrupted by a violent spasm, 

 on which strong shuddering contractions are super- 

 imposed. 



8. Nicotin. — On dropping Sarsia into a sea-water 

 solution of nicotin of appropriate strength, the 

 animal iuimediately goes into a violent and con- 

 tinuous spasm, on which a number of rapidly suc- 

 ceeding minute contractions are superimposed. 

 The latter, however, rapidly die away, leaving the 

 nectocalyx still in strong and continuous systole; 

 tentacles and manubrium are retracted to the 

 utmost. Shortly after cessation of spontaneity, 

 the bell is no longer responsive to tentacular stimu- 

 lation, but remains for a considerable time respon- 

 sive to direct stimulation of its own substance; 

 eventually, however, all irritability disappears, 

 while the tentacles and manubrium relax. On 

 transferring tlie animal to normal w^ater, muscular 

 irritability first returns, and then central, as shown 

 by the earlier response of the bell to direct than to 

 tentacular stimulation ; but if the animal has been 

 poisoned heavily enough to have had its muscular 

 iri'itability suspended, it is a long time before 

 central irritability returns. Soon after central 

 irritability has returned, the animal begins to shoAV 

 feeble signs of spontaneit}^ the motions being 

 exceedingly weak, with long intervals of repose ; 

 but the degree of such feebleness depends on the 

 length of time during wdiich the animal has pre- 

 viously been exposed to the poison ; thus in a speci- 

 men which had been removed from the poison 

 immediately after the disappearance of reflex 



