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