I think the object of these movements is probably that of stinging the offending body by means of the urticating cells with which the extremity of the manubrium is armed. But, be the object what it may, the fact of these movements occurring is a highly important one in connection with our study of the distribution of nerves in Medusæ, and the first point to be made out with regard to these movements is clearly as to whether or not they are truly of a reflex character. Accordingly, I first tried cutting off the margin, and then irritating the muscular tissue of the bell; the movements in question were performed exactly as before. I was thus led to think it probable that the reflex centres of which I was in search might be seated in the manubrium. Accordingly, I cut off the manubrium, and tried stimulating its own substance directly. I found, however, that no matter how small a portion of this organ I used, and no matter from what part of the organ I cut it, this portion would do its best to bend over to the side which I irritated. Similarly, no matter how short a stump of the manubrium I left in connection with the nectocalyx, on irritating any part of the latter, the stump of the manubrium would deflect itself towards that part of the bell, although, of course, from its short length it was unable to reach it. Hence there can be no doubt that every portion of the manubrium--down, at least, to the size which is compatible with conducting these experiments--is independently endowed with the capacity of very precisely localizing a point of irritation which is seated either in its own substance or in that of the bell.
We have here, then, a curious fact, and one which it will be well to bear in mind during our subsequent endeavours to frame some sort of a conception regarding the nature of these primitive nervous tissues. The localizing function, which is so very efficiently performed by the manubrium of this Medusa, and which if anything resembling it occurred in the higher animals would certainly have definite ganglionic centres for its structural co-relative, is here shared equally by every part of the exceedingly tenuous contractile tissue that forms the outer surface of the organ. I am not aware that such a diffusion of ganglionic function has as yet been actually proved to occur in the animal kingdom, but I can scarcely doubt that future investigation will show such a state of things to be of common occurrence among the lower members of that kingdom.[16]