the movement is always toward the centre of the leaf; and this also takes place, as we have seen, when an exciting object is lodged at the centre.  But when the object is placed upon either half of the leaf, the impulse radiating thence causes all the surrounding untouched tentacles to bend with precision toward the point of excitement, even the central tentacles, which are motionless when themselves charged, now responding to the call.  The inflection which follows mechanical irritation or the presence of any inorganic or insoluble body is transient; that which follows the application of organic matter lasts longer, more or less, according to its nature and the amount; but sooner or later the tentacles resume their former position, their glands glisten anew with fresh secretion, and they are ready to act again.

As to how the impulse is originated and propagated, and how the movements are made, comparatively simple as the structure is, we know as little as we do of the nature of nervous impulse and muscular motion.  But two things Mr. Darwin has wellnigh made out, both of them by means and observations so simple and direct as to command our confidence, although they are contrary to the prevalent teaching.  First, the transmission is through the ordinary cellular tissue, and not through what are called the fibrous or vascular bundles.  Second, the movement is a vital one, and is effected by contraction on the side toward which the bending takes place, rather than by turgescent tension of the opposite side.  The tentacle is pulled over rather than pushed over.  So far all accords with muscular action.

The operation of this fly-catching apparatus, in any case, is plain.  If the insect alights upon the disk of the leaf, the viscid secretion holds it fast—­at least, an ordinary fly is unable to escape—­its struggles only increase the number of glands involved and the amount of excitement; this is telegraphed to the surrounding and successively longer tentacles, which bent over in succession, so that within ten to thirty hours, if the leaf is active and the fly large enough, every one of the glands (on the average, nearly two hundred in number) will be found applied to the body of the insect.  If the insect is small, and the lodgment toward one side, only the neighboring tentacles may take part in the capture.  If two or three of the strong marginal tentacles are first encountered, their prompt inflection carries the intruder to the centre, and presses it down upon the glands which thickly pave the floor; these notify all the surrounding tentacles of the capture, that they may share the spoil, and the fate of that victim is even as of the first.  A bit of meat or a crushed insect is treated in the same way.

This language implies that the animal matter is in some way or other discerned by the tentacles, and is appropriated.  Formerly there was only a presumption of this, on the general ground that such an organization could hardly be purposeless.  Yet, while such expressions were natural, if not unavoidable, they generally were used by those familiar with the facts in a half-serious, half-metaphorical sense.  Thanks to Mr. Darwin’s investigations, they may now be used in simplicity and seriousness.