ME. G-. J. EOMANES ON THE LOCOMOTOE SYSTEM OE MEDUSAE. 
301 
sea-water the blocking is gradually overcome, and eventually every trace of it dis- 
appears. This experiment was suggested to me by Dr. Burdon Sanderson*. 
The contractile wave may be blocked by poisons in another way. A glance at Plate 33 
will show that a circumferential strip cut from the gonocalyx of Aurelia aurita is 
pervaded transversely by a number of nutrient tubes, which have all been cut through 
by the section. At the side of the strip, therefore, furthest from the margin there are 
situated a number of open ends of these nutrient tubes. Now on injecting any of the 
narcotic poisons into one of these open ends, the fluid of course permeates the whole 
tube, and the contractile wave becomes blocked at the transverse line occupied by the 
tube as effectually as if the contractile strip had been cut through at that line. 
A glance at Plate 32, again, will show that each lithocyst is surrounded by one of these 
nutrient canals. Upon injecting this canal, therefore, in a contractile strip, the effect 
of the poison may be exerted on the lithocyst more specially than it could be by any 
other method of administration. In view of recent observations concerning the effects of 
curare on the central nervous masses of higher animals, it may be worth while to 
state that a discharging lithocyst of Aurelia aurita , when thus injected with curare, 
speedily ceases its discharges. This fact alone, however, would not warrant any very 
trustworthy conclusions as to the influence of curare upon discharging centres ; for it is 
within the limits of possibility that the paralyzing effects may here be due to the 
influence of the poison on the surrounding contractile tissue. 
It is interesting to observe that if the discharging lithocyst be injected with chloro- 
form, or a not too strong solution of morphia, it recovers in the course of a night, while 
with alcohol the first effects of the injection are considerably to accelerate the frequency 
and to augment the potency of the discharges ; but the subsequent effects are a gradual 
diminution in the frequency and the vigour of these discharges until eventually total 
quiescence supervenes. In the course of a few hours, however, the torpidity wears 
away, and finally the medusid returns to its normal state. 
VI. General Summary. 
There is very good analogical reason to expect, that, in the case of the naked-eyed 
Medusae, the exclusive localization of centres of spontaneity in the margins of nectocalyces 
will be found to be a very general, if not a constant, feature in the anatomy of the entire 
group. In six of the most divergent genera that occur in this group I have found it 
to be almost uniformly true that excision of the entire periphery of a nectocalyx is 
* In conducting this experiment care must be taken not to exert the slightest pressure on any part of the 
strip (see IY. § 2 ( e ) p. 295). The method I adopted, therefore, was to have a vessel with a very deep furrow on 
each of its opposite lips. Upon filling this vessel to the level of these furrows with the poisoned water, and 
then immersing the whole vessel in ordinary sea-water up to the level of its brim, some of the poisoned water 
of course passed through the open furrows. The external body of water (i. e, the normal sea-water containing 
the animal) was therefore made proportionally very large, so that the slight escape of poison into it did not 
affect the experiment. On now passing the portion of the strip to he poisoned through the two opposite furrows 
it, was allowed to soak in the poison while freely floating, and so without suffering pressure in any of its parts. 
MDCCCLXXVI. 2 U 
