736 
ME. G. J. EOMANES ON THE LOCOMOTOE SYSTEM OE MEDUSAE. 
YI. POISONS. 
The last subject of which I shall treat in the present communication is the effects 
of various muscle- and nerve-poisons on the locomotor system of Medusae. In my former 
paper I dealt briefly with this subject; but, having this year bestowed a considerable 
amount of additional labour upon it, I shall now discuss it at somewhat greater length. 
The subject appears to me one of considerable importance, seeing that the effects of the 
muscle- and nerve-poisons have never, as yet, been systematically tried on the Medusae — 
animals that present us with the earliest appearance both of muscle and of nerve. I make 
this remark in order to excuse myself for burdening this already over-lengthy paper with 
a number of additional facts, which will be of interest only to the physiologist. 
§ 1. Chloroform. — My observations with regard to the distribution of nerves in Sarsia 
led me to investigate the order in which these connexions are destroyed, or temporarily 
impaired, by anaesthetics. The results, I think, are worth recording. In Sarsia , then, 
the following phases always mark the progress of anaesthesia by chloroform &c. : — 
1. Spontaneity ceases, as described in my former paper. 2. On now nipping a tentacle, 
pulling the polypite, or irritating the bell, a single locomotor contraction is given in 
answer to every stimulation. (In the unanaesthesiated animal a series of such contrac- 
tions would be the result of such stimulation.) 3. After locomotor contractions can no 
longer be elicited by stimuli, nipping a tentacle or the margin of the bell has the effect 
of causing the polypite to contract. 4. After stimulation of any part of the nectocalyx 
(including tentacles) fails to produce response in any part of the organism, the polypite 
will continue its response to stimuli applied directly to itself. 
§ 2. Nitrite of Amyl. — On Sarsia the effect of this agent is much the same as that 
of chloroform — the description just given in § 1 being quite as applicable to the effects 
of the nitrite as to those of chloroform. Before the loss of spontaneity supervenes, the 
rate of the rhythm is increased, while the strength of the pulsations is diminished. 
Tiaropsis diademata, from the fact of its presenting a very regular rhythm and being 
but of small size, is a particularly suitable species upon which to conduct many experi- 
ments relating to the effects of poisons. On this species the nitrite in appropriate (i. e. 
in very small) doses first causes irregularity and enfeeblement of the contractions, 
together with quickening of the rhythm. After a short time, a gradual cessation of the 
swimming-motions becomes apparent — these motions dying out more gradually, for 
example, than they do under the influence of chloroform. Eventually each pulsation is 
marked only by a slight contraction of the muscular tissue in the immediate neighbour- 
hood of the margin. If the dose has been stronger, however, well-marked spasmodic 
contractions come on and obliterate such gradual working of the poison. In all cases 
irritability of all parts of the animal persists for a long time after entire cessation of 
spontaneous movements — perhaps for three or four minutes in not over-poisoned 
animals ; but eventually it too disappears. On being now transferred to normal sea- 
water, the process of recovery is slower than it is after anaesthesiation by chloroform. 
It is interesting, moreover, to observe, that just as the power of coordination was 
