SECTION OF COVERED-EYED MEDUSA 99 



sudden, as if tlie distant lobe had then for the first 

 time received the stimulus. Moreover, one lobe — 

 usually one of those adjacent to the lobe directly 

 irritated — responds before the other two, and then 

 a variable time afterwards the latter also respond. 

 This time is, in most cases, comparatively short, the 

 usual limits being from a quarter of a second to two 

 seconds. How much of these enormous intervals is 

 occupied by the period of ganglionic latency, and 

 how much by that of transmission, it is impossible 

 to say; but I have determined that the rate of 

 transmission from the end of a lobe of the manu- 

 brium to a lithucyfc>o (deducting a second for the 

 double period of latent stimulation) is the same 

 as the rate of a tentacular wave, viz. nine inches a 

 second. The presumption, therefore, is that the 

 immense lapse of time required for reflex response 

 on the part of the manubrium is required by the 

 lobular ganglia, or whatever element it is that here 

 performs the ganglionic function. 



Exhaustion, 



In various modes of section of Aurelia I have 

 several times observed a fact that is worth record- 

 ing. It sometimes happens that w^hen the con- 

 necting isthmus between two almost severed areas 

 of excitable tissue is very narrow, the passage of 

 contraction-waves across the isthmus depends upon 

 the freshness, or freedom from exhaustion, of the 

 tissue which constitutes the isthmus. That is to 

 say, on faratlizing one of the two tissue-areas which 



