MB. Gr. J. EOMANES ON THE LOCOMOTOE SYSTEM OF MEDTJS^E. 
691 
(c) Temperature . — Returning now to the period of latent stimulation in Aurelia 
aurita, we have seen how profoundly this period is modified by the staircase effect we 
have just been considering. We have next to contemplate the influence of tempera- 
ture on the latent period and on the character of the contractions. But before 
stating my results, I may observe that in all my experiments in this connexion I 
changed the temperature of the Medusse 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 
effects 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 deganglionated tissues of Aurelia aurita 
as affected by temperature. 
Temperature of water (Falir.). 
Period of latent stimulation. 
70° 
1 second 
50° 
T second 
35° 
■| second 
20° 
y second 
In the case 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 1^ second ; 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. 
I may as well state here that in water at all temperatures, within the limits where 
responses to stimuli are given at all, the staircase action admits of being equally well 
produced. But in order to procure the maximum effect for any given temperature, the 
rate at which the successive stimuli are thrown in must be quicker in warm than in cold 
water ; for in cold water the latent period and the subsequent contraction are both so 
prolonged, that summation of the contractions is produced by employing such inter- 
vals between the successive shocks as yield the maximum staircase effect in warmer 
water. 
(B) Tetanus . — The allusion just made to summation of contractions leads us next to the 
subject of tetanus. As stated in my previous paper, some of the Medusae, when subjected 
to faradaic stimulation, respond, not by a single prolonged tetanus, but by a flurried series 
of rapidly alternating contractions and relaxations. It must now be added that these 
remarks apply especially to Sarsia ; for I find that in the case of Aurelia tolerably 
MDCCCLXXYII. 5 E 
