738 
ME. a. J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDUSAE. 
condition of exalted reflex irritability ; for its response to a single stimulus consists not 
merely, as in the unpoisoned animal, of a single spasm, but also, immediately after this, 
of a series of convulsive movements somewhat resembling swimming-movements destitute 
of coordination. If the strength of the solution be now again increased, a stage of deeper 
aneesthesiation may be produced, in which the Medusa will only respond to each stimu- 
lation by a single spasm. In still stronger solutions the only response is a single feeble 
contraction ; while in a nearly saturated solution the animal does not respond at all. 
But even from a saturated solution Tiaropsis diademata will recover when transferred 
to unpoisoned water. 
§ 4. Strychnia . — In my former paper I confined my remarks with reference to 
strychnia to the effects of this poison on a species of covered-eyed Medusa. It seems 
desirable, therefore, to supplement these remarks with a few additional ones regarding 
the effects of this poison on the naked-eyed Medusae. In the case of Sarsia the symp- 
toms of strychnia-poisoning are not well marked, from the fact that in this species con- 
vulsions always take the form of locomotor contractions. The symptoms, however, are 
in some respects anomalous. They are as follows : — First of all the swimming-motions 
become considerably accelerated, periods of quiescence intervening between abnormally 
active bouts of swimming. By-and-by a state of continuous quiescence comes on, 
during which the animal is not responsive to tentacular irritation, but remains so to 
direct muscular irritation, giving one response to each direct stimulus. The tentacles 
and polypite are much relaxed. In a sea-water solution just strong enough to taste 
bitter, this phase may continue for hours ; in fact till a certain opalescence of the con- 
tractile tissues — which it is a property of strychnia, as of most other reagents, to produce 
— has advanced so far as to place the tissues beyond recovery. If the exposure to such 
a solution has not been very prolonged, recovery of the animal in normal water is rapid. 
In a specimen exposed for 2^ hours to such a solution, recovery began in half an hour 
after restoration to normal water, but was never complete. In all cases, if the poisoning 
is allowed to pass beyond the stage at which response to direct muscular irritation ceases, 
the animal is dead. 
On Tiaropsis indicans this poison has the effect of causing a general spasm, which 
would be undistinguishable from that which in this species results from general stimu- 
lation of any kind, were it not that there is a marked difference in one particular. For 
in the case of strychnia-poisoning the spasm, while it lasts, is not of uniform intensity 
over all parts of the nectocalyx ; but now one part and now another part or parts are in a 
state of stronger contraction than other parts, so that, as a general consequence, the outline 
of the nectocalyx is continually changing its form. Moreover, in addition to these com- 
paratively slow movements, there is a continual twitching observable throughout all parts 
of the nectocalyx. Each individual twitch only extends over a small area of the con- 
tractile tissue ; but in their sum their effect is to throw the entire organ into a sort of 
shivering convulsion, which is superimposed on the general spasm. After a time the 
latter somewhat relaxes, leaving the former still in operation, which, moreover, now 
