300 
MR. &. J. ROMANES ON THE LOCOMOTOR SYSTEM OF MEDUSAE. 
body which ensues is totally different from that of an ordinary locomotor contraction, 
all parts folding together in one very strong and long-protracted systole, after which the 
diastole is very much slower than usual. Well, on nipping any portion of the poisoned 
half of Staurophora laciniata, this half remained absolutely motionless, while the 
unpoisoned half, though far away from the seat of irritation, immediately ceased its 
normal contractions, and folded itself together in the very peculiar and distinctive 
manner just described. This observation was repeated a number of times, and, when 
once the requisite strength of the curare solution had been obtained, always with the 
same result. The most suitable strength I found to be 1 in 2500, in which solution 
the poisoned half required to soak for half an hour. 
I also tried the effect of this poison on the covered-eyed Medusse, and have 
fairly well satisfied myself that its peculiar influence is likewise observable in the case 
of this group. 
It has further to be stated that when the poisoned half is again restored to normal 
sea-water, the effects of curare pass off with the same astonishing rapidity as is observ- 
able in the case of the other poisons which I have tried. Thus, although an exposure 
of half an hour to the influence of curare of the strength named is requisite to destroy 
the motor power in the case of Staurophora laciniata , half a minute is sufficient to 
ensure its incipient return when the animal is again immersed in unpoisoned water. 
It is also to be observed that a very slight degree of ower-poisoning paralyzes the 
transmitting system as well as the responding one ; so that if any one should repeat my 
observation, I must warn him against drawing erroneous conclusions from this fact. Let 
him use weak solutions with prolonged soaking, and by watching when the voluntary 
motions in the poisoned half first cease, he need experience no difficulty in obtaining 
results as decided as it is possible for him to desire. 
I think it would be difficult to overrate the importance of these results : to my mind 
they are perhaps the most interesting which are contained in this paper. They not only 
prove that curare poison is consistent in manifesting its remarkable property when 
applied to these the lowest forms of life that present the beginnings of a nervous system ; 
but they prove what is far more important, that in animals which, as we have seen from 
other evidence, present us with the first indications of a nervous system, the latter 
appears to have already undergone a differentiation in its functions, such that it is 
capable not only of influencing contiguous contractile parts, but also of being influenced 
by distant excitable parts. 
( e ) I shall conclude all I have to say at the present time upon the subject of poisons 
by stating the interesting fact, that if any of the narcotic or aneesthesiating agents 
be administered to any portion of a contractile strip cut from the gonocalyx of 
Aurelia aurita in the way already described, the rate of the contractile waves is 
at first progressively slowed (I shall give the actual tracings in a future paper), and 
eventually their passage is completely blocked at the line where the poisoned water 
begins. Upon now restoring the poisoned portion of the contractile strip to normal 
