21G JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



SarsiiB never respond to a single stimulus with 

 more than a single contraction, these multiple 

 responses must, I think, be ascribed to a state of 

 exalted reflex irritability. After a long exposure 

 to the poison, however, only a single response is 

 given to each stimulus ; and still later all irritability 

 ceases. On now transferring the Sarsise to un- 

 poisoncd water, recovery is effected even though 

 the previous exposure has been of immensely long 

 duration, e.g. an hour. 



An interesting point with regard to caffein- 

 poisoning of Sarsia is, that as soon as spontaneity 

 ceases the tentacles and manubrium lose their tonus 

 and become relaxed to their utmost extent. This 

 is not the case with an^sthesiation by chloroform, 

 even when pushed to the extent of suspending 

 irritability. If, however, Sarsise which have been 

 auDOsthesiated to this extent in chloroform be 

 suddenly transferred to a solution of caffein, the 

 tentacles and manubrium may soon be seen to relax, 

 and eventually these organs lose their tonus as 

 completely as if the anaesthesia had from the first 

 been produced by the ca'Iein. Moreover in this 

 experiment the irritaljility, which had been de- 

 stro^^ed by the chloroform, returns in the solution 

 of caiFijin — provided the latter be not quite satu- 

 rated — though spontaneity of course remains sus- 

 pended throughout. 



The eifects of graduating the doses of caffein may 

 be stated in connection with another species, viz. 

 Tiaropsis diademata. In a weak solution the effects 

 are a quickening of the pulsations (e.g. from C4 to 



