The fusca has the longest arms, and makes use of the most curious manceuvres to seize its prey. They are best viewed in a glass seven or eight inches deep, when their arms commonly hang down to the bottom. When this or any other kind is hungry, it spreads its arms in a kind of circle to a considerable extent, inclosing in this, as in a net, every insect which has the misfortune to come within the circumference. While the animal is contracted by seizing its prey, the arms are observed to swell like the muscles of the human body when in action. Though no appearance of eyes can be observed in the polype, they certainly have some knowledge of the approach of their prey, and skew the greatest attention to it as soon as it conies near them. It seizes a worm the, moment it is touched by one of the arms ; and in conveying it to the mouth, it frequently twists the arm into a spiral, like a cork-screw, by which means the insect is brought to the mouth in a much shorter time than otherwise it would be ; and so soon are the insects on which the polypes feed killed by them, that M. Fontana thinks they must con tain the most powerful kind of poison ; for the lips scarcely touch the animal when it expires, though there cannot be any wound perceived on it when dead. The worm, when swallowed, appears sometimes single, sometimes double, ac cording to circumstances. When full, the polype contracts itself, hangs down as in a kind of stupor, but extends again in proportion as the food is digested, and the excrementitious part is The manner in which the polypes gene rate is most perceptible in the grisca and fusca, as being considerably larger than the viridis. If we examine one of them in summer, when the animals are most active, and prepared for propagation, some small tubercles will be found pro ceeding from its sides, which constantly increase in bulk, until at last in two or three days they assume the figure of small polypes. When they first begin to shoot, the excrescence becomes pointed, assuming a conical figure, and deeper colour than the rest of the body. In a short time it becomes truncated, and then cylindrical, after which the arms begin to shoot from the anterior end. The tail adheres to the body of the parent animal, but gradually grows smaller, until at last it adheres only by a point, and is then ready to be separated. When this is the case, both the mother and young ones fix themselves to the sides of the glass, and are separated from each other by a sud den jerk. The time requisite for the formation of the young ones is very dif ferent, according to the warmth of the weather, and the nature of the food eaten by the mother. Sometimes they are fully
formed, and ready to drop off, in twenty four hours; in other cases, when the weather is cold, fifteen days have been requisite for bringing them to perfection. The polypes produce young ones indis criminately from all parts of their bodies, and five or six young ones have frequent ly been produced at once ; nay, M. Trembley has observed nine or ten pro duced at the same time. Nothing like copulation among these creatures was ever observed by M. Trembley, though for two years he had thousands of them under his inspection.
When a polype is cut transversely, or longitudinally, into two or three parts; each part in a short time becomes a per fect animal ; and so great is this prolific power, that a new animal will be pro duced even from a small portion of the skin of the old one. If the young ones be mutilated while they grow upon the parent, the parts so cut off will be repro. duced ; and the same property belongs to the parent. A truncated portion will send forth young ones before it has ac quired a new head and tail of its own, and sometimes the head of the young one supplies the place of that which should have grown out of the old one. If we slit a polype longitudinally through the head to the middle of the body, we shall have one formed with two heads ; and by again slitting these in the same manner, we may form one with as many heads as we please. A still more surprizing pro perty of these animals is, that they may be grafted together. If the truncated por tions of a polype be placed end to end, and gently pushed together, they will unite into a single one. The two portions are first joined together by a slender neck, which gradually fills up and disap pears, the food passing from one part into the other : and thus we may form polypes, not only from different portions of the same animal, but from those of dif ferent animals. We may fix the head of one to the body of another, and the com pound animal will grow, eat and multiply, as if it had never been divided. By push ing the body of one into the month of an other, so far that their heads may be brought into contact, and kept in that situation for some time, they will at last unite into one animal, only having dou ble the usual number of arms. The hy dra fusca may be turned inside out like a glove, at the same time that it continues to eat and live as before. The lining of the stomach now forms the outer skin, and the former epidermis constitutes the lining of the stomach. See Adams on the Microscope.