62 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 
Medusz by drawing off the water in which they 
floated with a siphon, while at the same time I 
substituted water of a different temperature from 
that which I thus abstracted. In this way, without 
modifying any of the other conditions to which the 
animals were exposed, I was able to observe the 
efiects of changing the temperature alone. 
With regard to the effect of temperature on the 
latent period of stimulation, the following table, 
setting forth the results of one among several 
experiments, explains itself. 
Period of latent stimulation of the deganglio- 
nated tissues of Aurelia aurita as affected by tem- 
perature :— 
Temperature of water (Fahr.). Period of latent stimulation. 
70° } second 
50° 4 second 
35° 2 second 
2U° } second 
In the ease of each observation, several shocks 
were administered before the latent period was 
taken, in order to decrease this period to its 
minimum by the staircase action. When this is 
not done, the latent period at 20° may be as long 
as 12 seconds; but soon after this irritability 
disappears. 
The extraordinary sluggishness of the latent 
period at very low temperatures is fully equalled 
by the no less extraordinary sluggishness of the 
contraction. 
