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



rence of a gradually increasing spasm, which differs 

 from a normal spasm in the respects already de- 

 scribed under stryclmia. In all the species both of 

 Sarsia and Tiaropsis, the manubrium and tentacles 

 are retracted during exposure to this poison. 



BeriiarJcs. 



The above comprises all the poisons which I have 

 tried, and I think that all the observations taken 

 too'ether show a wonderful des^ree of resemblance 

 between the actions of the various poisons on the 

 Med usee and on the hio-her animals — a c^eneral fact 

 which is of interest, when we remember that in 

 these nerve-poisons we possess, as it were, so many 

 tests Avherewith to ascertain whether nerve-tissue, 

 where it first appears upon the scene of lif'e, presents 

 the same fundamental properties as it does in the 

 hiojher animals. And these observations show that 

 such is the case. When the physiologist bears in 

 mind that in Sarsia w^e have the means of testing 

 the comparative inlluence of any poison on the 

 central, peripheral, and muscular systems respec- 

 tively,* he will not fail to appreciate the signifi- 

 cance of these observations. In reading over the 

 whole list he will meet with an anomaly here and 



* The method of comparison consists, as will already have been 

 gather-ed from the perusal of the foregoing sections, in : — fir.-t, 

 sl.iinnlating the tentacles, and observing whether this is followed 

 by such a discharge of the attached ganglion as causes tlie bell to 

 contract ; next, stimulating the bell itself, to ascertain whether 

 the muscular irritability is impaired ; and, lastly, stimulating 

 either the tontacles or the bell, to observe whether the reciprocal 

 connections between tentacles, bell, and manubrium arenuiiiiured. 



