ME. G. J. EOMANES ON THE LOCOMOTOE SYSTEM OF MEDUSA. 
722 
peripheral zones, I think it may fairly be said that the conductile power of the latter 
is greater than that of the former ; for otherwise the above experiments ought to yield 
a large majority of races won by the waves that course through the central zones ; and 
this is not the case. Indeed it is surprising how often the race is, as it were, neck and 
neck, thus showing that the relative conductivity of all the zones is precisely adjusted 
to their relative lengths; and forasmuch as in the unmutilated animal this adjustment 
must clearly serve the purpose of securing to the contractile waves a passage of uniform 
rate over the whole radius of the umbrella, I doubt not that if it were possible to perform 
the racecourse section without interrupting any of the lines of conductile tissue, neck 
and neck races would be of invariable occurrence. It may be added that all the above 
results are observable when the discharges of a single remaining lithocyst are substituted 
for artificial stimuli at the undivided end of a strip. 
(d) Interdigitating cuts, as might be expected, prolong the time of contractile 
waves in their passage through the tissue in which the cuts are interposed. For 
example, in a spiral strip measuring 26 inches in length, the time required for the 
passage of a contractile wave from one end to the other is represented by the line a b 
in the annexed woodcut. But after twenty interdigitating cuts had been interposed, 
ten on each side of the strip, the time increased to c d — the line e f representing one 
second. And more severe forms of section are, of course, attended with a still more 
retarding influence. 
Fig. 12. 
( e ) The effects of temperature on the rate of contractile waves are very striking. For 
instance, in a rather narrow strip measuring 28 inches long and 1^ inch wide, the following 
variations in rate occurred : — 
Temperature of water. 
Time occupied in passage of 
contractile waves. 
26° 
4 seconds. 
32° 
3 seconds. 
42° 
2J- seconds. 
65° 
2 seconds. 
7^° 
1|- second. 
85° 
Blocked. 
Or, adopting again the graphic method of statement, these variations may be repre- 
sented as follows : — 
