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



pulsations supervene. This irregularity then in- 

 creases more and more, till at length it groAvs into 

 well-marked convulsions. The convulsions manifest 

 themselves in the form of extreme deviations from 

 the rhythmical contractions so characteristic of 

 Cyan?ea capillata. Instead of the heart-like regu- 

 larity with which systole and diastole follow one 

 another in the unpoisoned animal, we now have 

 periods of violent and prolonged systole resembling 

 tonic spasm ; and when the severity of this spasm 

 is for a moment abated, it is generally renewed 

 before the umbrella has had time a!2'-ain to become 

 fully expanded. Moreover, the spasm itself is not 

 of uniform intensity throughout the time it lasts ; 

 but while the umbrella is in a continuously 

 contracted state, there are observable a perpetual 

 succession of extremely irregular oscillations in the 

 strength of the contractile influence. It is further 

 a highly interesting fact that the convulsions are 

 very plainly of a iiaroxysvial nature. After the 

 umbrella has suffered a prolonged period of con- 

 vulsive movements, it expands to its full dimensions, 

 and in this form remains for some time in a state 

 of absolute quiescence. Presently, however, another 

 paroxysm supervenes, to be followed by another 

 ])eriod of quiescence, and so on for hours. The 

 periods of quiescence are usually shorter than are 

 those of convulsion; for while the former seldom 

 last more than forty seconds or so, the latter may 

 continue uninterruptedly for live or six minutes. In 

 short, Medusce, when submitted to the influence of 

 str^'chnia, exhibit all the syinptoms of strychnia 



