174 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 
Eventually the swimming motions entirely cease ; 
but almost immediately after the animals are 
restored to normal sea-water, they recover them- 
selves completely, the rate and regularity of their 
rhythm being then quite natural. The suddenness 
with which this return to the normal state of 
things is effected cannot but strike the observer as 
very remarkable, and I may mention that it takes 
place with equal suddenness at whatever stage in 
the above-described process of asphyxiation the 
transference to normal sea- water is accomplished. 
