8G0 
MR. G. J. ROMANES AND PROEESSOR J. C. EWART 
pedicellarise on the other side of the line. This complete inability of a stimulus to 
escape round the ends of an injury, forms a marked contrast to the almost unlimited 
degree in which such escape takes place in the more primitive nervous plexus of the 
Medusae. 
Although the nervous connexions on which the spines and pedicellarise depend for 
their function of localising and closing round a seat of stimulation are thus shown to 
be completely destroyed by injury of the external plexus, other nervous connexions, 
upon which another function of the spines depends, are not in the smallest degree 
impaired by such injury. The other function to which we allude is that which brings 
about the general co-ordinated action of all the spines for the purposes of locomotion. 
That this function is not impaired by injury of the external plexus is proved by the 
fact that, if the area within a closed line of injury on the surface of the shell be 
strongly irritated, all the spines over the whole surface begin to manifest their peculiar 
bristling movements, and by this co-ordinated action rapidly move the animal in a 
straight line of escape from the source of irritation; the injury to the external plexus, 
although completely separating the spines enclosed by it from their neighbouring 
spines as regards what may be called their local function of seizing the instrument of 
stimulation, nevertheless leaves them in undisturbed connexion with all the other 
spines in the organism as regards what may be called their universal function of 
locomotion. 
(B.) Evidently, therefore, this more universal function must depend upon some 
other set of nervous connexions; and experiment shows that these are distributed 
over all the internal surface of the shell. Our mode of experimenting was to divide 
the animal into two hemispheres, remove all the internal organs of both hemispheres 
(these operations producing no impairment of any of the functions of the pedicels, 
spines, or pedicellarise), and then paint with strong acid the inside of the shell—com¬ 
pletely washing out the acid after about a quarter of a minute’s exposure. The results 
of a number of experiments conducted on this method may be thus epitomised :— 
The effect of painting the back or iuside of the shell with strong acid (e.g., pure 
HC1) is that of at first strongly stimulating the spines into bristling movements, 
and soon afterwards reducing them to a state of quiescence, in which they lie more or 
less flat, and in a peculiarly confused manner, that closely resembles the appearance of 
corn when “ laid ” by the which The spines have now entirely lost both them spon¬ 
taneity and their power of responding to a stimulus applied on the external surface of 
the shell— i.e., their local reflex excitability, or power of closing in upon a source of 
irritation, These effects may be produced over the whole external surface of the shell, 
by painting the whole of the internal surface ; but if any part of the internal surface 
be left unpainted, the corresponding part of the external surface remains uninjured. 
Conversely, if all the internal surface be left unpainted except in certain lines or 
patches, it will only be corresponding lines and patches on the external surface that 
