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



sec, in the various species of Tiaropsis, irritability 

 persists after cessation of the spontaneous contrac- 

 tions. In Sarsia the nervous connections between 

 the tentacles and manubrium, and also between the 

 tentacles themselves, are not impaired during the 

 time that the bell is motionless ; and even when 

 the irritability of the bell has quite disappeared as 

 regards any kind of stimulation, the manubrium 

 and tentacles will continue responsive to stimuli 

 applied either directly to themselves or to any 

 part of the neuro-muscular sheet of the bell. 



The convulsions due to the action of veratrium 

 are well marked in the various species of the genus 

 Tiaropsis. They consist of violent fluttering 

 motions without any co-ordination ; but there are 

 no spasms, as in the case of strychnia poisoning. 

 After the convulsions have lasted for some time, a 

 quiescent stage comes on, during which the animal 

 remains responsive to stimulation, though not ab- 

 normally so. Recovery in unpoisoned water is 

 rapid, the movements being at first marked by an 

 absence of co-ordination. 



6. Digitalin. — The first effect of this poison on 

 Sarsia is to quicken the swimming motions, and 

 then to enfeeble them progressively till they degene- 

 rate into mere spasmodic twitches. The manubrium 

 and tentacles are now strongly retracted, while the 

 nectocalyx is drawn together so as to assume an 

 elongated form. The latter is now no longer respon- 

 sive either to tentacular or to direct stimulation; 

 but the tentacles and manubrium both remain 

 responsive to stimuli applied either directly to 



