726 
ME. Gr. J. EOMANES ON THE LOCOMOTOE SYSTEM OF MEDUSAE. 
done so. The loss of time, however, appears to take place in the polypite 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 sympathetic response may be even more variable than this, the limits I have observed 
being as great as from three to ten seconds. In all cases, however, the response, when 
it does occur, is sudden, as if the distant lobe had then for the first time received the 
stimulus. Moreover one lobe — usually one of those adjacent to the lobe directly irri- 
tated — 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 polypite to a lithocyst (deducting a second for the double period of 
latent stimulation) is the same as the rate of a tentacular wave, viz. 9 inches a second. 
The presumption, therefore, is that the immense lapse of time required for reflex 
response on the part of the lobes is due to a prolonged period of latent stimulation on 
the part of the lobular ganglia, or whatever element it is that here performs the gan- 
glionic function. And, in any case, it may be remarked, this wonderful tardiness of 
response on the part of the polypite of Aurelia aurita is strikingly similar to that of 
Tiaropsis indicans , where the rate of transmission of a stimulus in the bell, though very 
slow, is rapid as compared with the time that elapses before the polypite makes its 
sudden crouching movement. Both these cases, it will be noticed, stand in marked 
contrast with that of Sarsia, where response by the polypite to irritation of the bell or 
tentacles is exceedingly rapid. 
Y. COOEDINATION. 
§ 1. Covered-eyed Medusae. — (a) From the fact that in the covered-eyed Medusae the 
passage of a stimulus-wave is not more rapid than that of a contractile wave, we may 
be prepared to expect that in these animals the action of the locomotor ganglia is not, 
in any proper sense of the term, a coordinated action ; for if a stimulus-wave cannot 
outrun a contractile wave, one ganglion cannot know that another ganglion has dis- 
charged its influence, till the contractile wave which results from a discharge of the 
active ganglion has reached the passive one. And this I find to be usually the case ; 
for, as previously stated, it may usually be observed that one or more of the lithocysts 
are either temporarily or permanently prepotent over the others, i. e. that contractile 
waves emanate from the prepotent lithocysts, and then spread rapidly over the swimming- 
bell, without there being any signs of coordinated, or simultaneous, action on the part of 
the other lithocysts. Nevertheless in many cases such prepotency cannot, even with the 
greatest care, be observed ; but upon every pulsation all parts of the swimming-bell seem 
to contract at the same instant. And this apparently perfect coordination among the 
eight marginal ganglia may continue for any length of time. I believe, however, that 
