This is, no doubt, as I have already observed, a very remarkable fact; but it becomes still more so when we have regard to the histological researches of Professor Schäfer on the structural character of this nerve-plexus. For these researches have shown that the nerve-fibres which so thickly overspread the muscular sheet of Aurelia do not constitute a true plexus, but that each fibre is comparatively short and nowhere joins with any of the other fibres; that is to say, although the constituent fibres of the network cross and recross one another in all directions--sometimes, indeed, twisting round one another like the strands of a rope--they can never be actually seen to join, but remain anatomically insulated throughout their length. So that the simile by which I have represented this nervous network--the simile, namely, of a sheet of muslin overspreading the whole of the muscular sheet--is, as a simile, even more accurate than has hitherto appeared; for just as in a piece of muslin the constituent threads, although frequently meeting one another, never actually coalesce, so in the nervous network of Aurelia, the constituent fibres, although frequently in contact, never actually unite. Now, if it is a remarkable fact that in a fully differentiated nervous network the constituent fibres are not improbably capable of vicarious action to almost any extent, much more remarkable does this fact become when we find that no two of these constituent nerve-fibres are histologically continuous with one another. Indeed, it seems to me we have here a fact as startling as it is novel. There can scarcely be any doubt that _some_ influence is communicated from a stimulated fibre _a_ to the adjacent fibre _b_ at the point where these fibres come into close apposition. But what the nature of the process may be whereby a disturbance in the excitable protoplasm of _a_ sets up a sympathetic disturbance in the anatomically separate protoplasm of _b_, supposing it to be really such--this is a question concerning which it would as yet be premature to speculate. But I think it may be well for physiologists to keep awake to the fact that a process of this kind probably takes place in the case of these nerve-fibres. For it thus becomes a possibility which ought not to be overlooked, that in the fibres of the spinal cord, and in ganglia generally, where histologists have hitherto been unable to trace any anatomical or structural continuity between cells and fibres, which must nevertheless be supposed to possess physiological or functional continuity--it thus becomes a possibility that in these cases no such anatomical continuity exists, but that the physiological continuity is maintained by some such process of physiological induction as probably takes place among the nerve-fibres of Aurelia.[14]