170 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 
irregular intervals, a contraction so feeble that it 
was restricted to the immediate vicinity of the 
lithocyst in which it originated. Soon after this 
stage irritability towards all kinds of stimuli entirely 
ceased, including even strong spirit dropped on the 
under surface of the animal when taken momentarily 
out of the water. All these stages thus described 
were passed through rapidly, the whole series occu- 
pying rather less than five minutes. On now leav- 
ing the specimen for ten minutes and then restoring 
it to its original water at 45°, all the above-men- 
tioned stages were passed through in reverse order. 
The first faint marginal contraction was confined to 
the immediate vicinity of the prepotent lithocyst, 
and all subsequent contractions continued to be so 
for the next three minutes. Rhythm very slow. 
Contractions now began to penetrate round the 
margin, and in eight minutes from the restoration 
had gone all the way round, the rate of their 
rhythm meanwhile increasing. In two minutes 
more all the umbrella was contracting at the rate 
of fifteen per minute. 
In another specimen, subjected to the same con- 
ditions, the rate of recovery was even more rapid, 
occupying only two minutes altogether; but in 
every case the process of recovery is a gradual one, 
and differs only in the time it occupies in passing 
through the various stages. 
Effects of Freezing Medusee. 
Tn conclusion, I will describe some rather interest- 
ing experiments that consisted in freezing some 
