876 
MR. G. J. ROMANES AND PROFESSOR J. C. EWART 
Echinus is now no longer able to escape from injury, but when stimulated crawls 
indifferently in any direction. Thus, removal of the nerve-centre seriously impairs the 
activity of the pedicels, and totally destroys their co-ordination. Yet when specimens 
so mutilated are inverted, one out of every four specimens is able to right itself. This, 
however, is only done with great difficulty and after a long time, so that, under these 
circumstances, the execution of this manoeuvre seems to be just barely possible. Still 
the fact of its being possible at all proves that the integrity of the nerve-centre is not 
absolutely essential to its performance. Therefore, as experiment has failed to reveal 
to us any other general nerve-centre in the animal, and as even a segment of the 
animal containing only a single row of pedicels is in many cases able to perform this 
manoeuvre, we conclude, as already stated, that the action of the pedicels is partly of 
a serial character, though largely assisted by the co-ordinating influence that emanates 
from the nerve-centre. 
The effect of this operation upon the spines and pedicellarice still remains to be 
considered. No effect at all is pi*oduced upon the pedicellarise ; but upon the spines a 
profound influence is seen to be exercised. Their spontaneity, indeed, remains un¬ 
impaired, as does also the function which they share with the pedicellarim of closing 
round any instrument of stimulation ; likewise their power of responsive bristling all 
over the animal when any part of the animal is severely stimulated continues to be 
manifested as before, although for an hour or two after the operation this power is 
suspended by shock. But the general co-ordination of the spines is totally and 
permanently destroyed; for if the animal be placed upon a table and a spirit lamp 
flame held against one side, although the spines will manifest their bristling move¬ 
ments (if the period of shock has been allowed to pass away), they will no longer 
co-operate to remove the animal from the source of irritation. These facts prove, 1st, 
that the general co-ordination of the spines is wholly dependent upon the nerve-centre ; 
2nd, that the spontaneity and local reflex irritability are wholly independent of that 
centre—they depend entirely upon the external nerve-plexus ; and 3rd, that the 
universal nervous connexions revealed in the bristling movements of the spines, and 
which as shown by previously narrated experiments depend upon the hypothetical 
internal nerve-plexus, are themselves in nervous connexion with the nerve-centre. 
For only thus can we explain the long period of shock which removal of this centre 
entails upon the functions of this supposed internal plexus. Nevertheless, the fact 
that these functions are eventually resumed in the general bristling of the spines, 
proves that this general communication between the spines is maintained by the direct 
conductibility of the supposed internal plexus, and is not of the nature of a reflex in 
which the nerve-ring is concerned as a general centre for the responsive, as dis¬ 
tinguished from the co-ordinated, action of the spines. 
