About two hours after I had been stung, I perceived that a vesicle had arisen on the spot; and when children have been stung, I observed that numerous small vesicles arose, similar to those produced by the nettle. The intensity of the effects produced depends on the size and consequent power of the animal; and after it has been for some time removed from the water, it is found that the stinging property has diminished. This irritative property, unattended, however, by any of the constitutional effects, remains for a long time in the tentaculæ, even after they have been removed from the animal; for on touching a handkerchief some weeks after it had been used in wiping off some portions of the tentaculæ, the stinging property was found to have remained, although it had lost that virulent quality, which produced on a recent application such violent constitutional irritation. This irritative secretion does not, however, exist solely in this species of mollusca; several of the _medusæ_ have similar properties, which may perhaps be considered as both offensive and defensive; and it has been, and no doubt correctly, supposed to be given to these animals as a means of procuring their food, the benumbing principle existing in the tentaculæ rendering their prey when touched unable to escape. For what purpose this acrid property is found existing in the vegetable kingdom, it is difficult to decide, and all that has yet been said on the subject may be considered as merely hypothetical. For instance, at the island of Singapore there is a remarkable species of the order Fuci, usually found growing in isolated patches upon coral banks. Finlayson thus mentions it: “It is pinnated, plumose, elegant, about a foot and a half in length, and of a whitish colour. It is endued with a property of stinging like nettles; the sensation produced is more acute and more penetrating, more instantaneous, but somewhat more permanent. The hand is scarcely brought into contact with it, before the wound is inflicted. A small corrugated granular bag, filled with a transparent fluid, would seem to be the organ by which it produces this effect. These are no sooner touched than they discharge the fluid they contain. The plant soon loses this power after being removed from the water.” This plant seems, therefore, to possess an offensive or defensive property analogous to that of the _Physalia_, but for what purpose it would be difficult to form an opinion.