98 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



In view of this anomaly, I was led to think that 

 if the rate of the stimulus-wave is dependent in 

 a large degree on the strength of the stimulus that 

 starts it, the slow rate of nine inches a second 

 might be more than doubled, if, instead of using a 

 stimulus so gentle as not to start a contraction- 

 wave, I used a stimulus sufficiently strong to do 

 this. Accordingly I chose a specimen of Aurelia 

 wherein the occurrence of tentacular waves was 

 very conspicuous, and found, as I. had hoped, that 

 every time I stimulated too gently to start a con- 

 traction-wave, the tentacular wave travelled only 

 at the rate of nine inches a second ; whereas, if I 

 stimulated with greater intensity, I could always 

 observe the tentacular wave coursing an inch or 

 two in front of the contraction-wave. 



It is remarkable, however, that in this, as in all 

 the other specimens of Aurelia which I experimented 

 upon, the reflex response of the manubrium was 

 equally long, whatever strength of stimulus I applied 

 to the umbrella ; or, at any rate, the time was only 

 slightly less when a contraction- wave had passed 

 than when only a tentacular wave had done so. 

 The loss of time, however, appears to take place in 

 the manubrium itself, where the rate of response 

 is astonishingly slow. Thus, if one lobe be irritated, 

 it is usually from four to eight seconds before the 

 other lobes respond. But the time required for 

 such sj^mpathetic response may be even more 

 variable than this — the limits I have observed 

 beino; as G:reat as from three to ten seconds. In all 

 cases, however, the response, when it does occur, is 



