288 
ME. G. J. EOMANES ON THE LOCOMOTOE SYSTEM OE MEDUSAE. 
On again trying induced current, no contraction. On again trying direct current, 
strong contractions [thus far, of course, the behaviour of the tissue was normal, see 
above § 2 (A)], and after four or five of these, shivering began ; this lasted for four 
minutes, and, when again quiescent, the bell again responded to make and break of 
direct current in the ordinary way.” 
Now all that can be gathered from these and similar notes is, that the shivering 
motion in question may be started either by the direct or by the induced current, and 
this in some cases when the bell has repeatedly refused to answer stimuli in the ordi- 
nary way. It may further be gathered from these notes that shivering is most likely 
to begin after the bell has received a number of shocks in succession. I must also 
state that it is almost certain to ensue upon slightly acidulating the water in which the 
mutilated bell is suspended. The shivering, if it begins under these circumstances, 
will then continue for some time even after the bell is restored to normal sea-water. 
§ 3. Chemical Stimulation. — Under this heading I have very little to say, for the 
simple reason that the excitable tissues of Medusae conform in every respect to the 
rules which are followed by the nervo-muscular tissues of higher animals. Both the 
severed locomotor centres and the mutilated swimming-organs, as well, I may add, as 
several polypites and tentacles, respond to applications of various acids, solutions of 
various metallic salts, alcohol, ether, glycerine, &c. It may here be stated that fresh 
water is quickly fatal to Medusse, especially in the case of the naked-eyed group. This 
latter fact has been previously observed by Agassiz. 
§ 4. Thermal Stimulation. — For the present I reserve my observations relating to 
this subject. 
IV. Section. 
§ 1. Amount of section which the contractile tissues of Medusae will endure without 
suffering loss of their physiological continuity. — The extent to which the substance of 
the swimming-organs of Medusae may be mutilated without undergoing destruction of 
their physiological continuity is in the highest degree astonishing. Again taking Sarsia 
as a type of the naked-eyed division, I shall here 
describe two modes of section which are the most trying 
that I was able to devise. 
(a) Suppose the annexed diagram to represent Sarsia 
in projection, the lines being cuts. It will be seen that 
there are two systems of interdigitating cuts, with four 
radial cuts in each system. Those of the one system 
pass from the margin to two thirds of the way up the 
cone, while those of the other system pass . in the form 
of a cross from the apex of the cone to two thirds of 
the way towards its base. It will thus be evident that a 
stimulus to contraction originating in any point a of the margin cannot radiate its 
influence throughout the whole contractile substance of the bell, except by traversing 
