Baron Gleichen tinged water with carmine, and mix ed it with an infusion. On the second day, the internal colour of the animalcula sheaved, that most of them had swallowed part of the liquid.
Of all the peculiarities by which animalcula are dis tinguished, those which respect their propagation are the best deserving of attention. The concourse of the sexes is required to perpetuate the species among. the larger animals; but, on descending the scale, some are found which individually possess the characteristics of both sexes united in themselves, though their con course is still required. In some, such as fishes, each possesses the sexual organs of the male or female; but instead of their concourse, external fecundation takes place : and others again, such as the animal flower and polypus, are strictly hermaphrodites; and all produce their young without actual fecundation. The animal cula infusoria propagate by eggs, by living foetuses, and by a portion of the body being detached from the body of the parent. Whether they have any union of, the sexes, like the larger animals, is keenly contested. Roffredi denies the copulation of animalcula in general, though he admits that of microscopic eels. Muller re lates several instances of it ; and he affirms that it has continued two hours in the paramecium aurelia. Spal lanzani put the egg of an animalcule into a watch glass; ;.t rroduced an animalcule ; which, though isolated, laid eggs, and from these came fertile animalcula. On his isolating the young of viviparous animalcula, they pro duced a fertile offspring. He never witnessed the copu lation of animalcula during his numerous observations, but he does not deny the possibility of it. Therefore, it is most likely, amidst all the varieties of their propaga tion, that it does take place.
Animalcula also multiply, by a spontaneous division of the body, into two or more parts. This singular mode of propagation was first ascertained by M. de Saussure, and has been further investigated by succeeding natu ralists. If an animalcula, propagating in this manner, is isolated in a watch glass, the traces of a contraction around the middle of the body become visible, which marks incipient division. The stricture soon increases insensibly, and the animal then somewhat resembles a blown bladder tied tight•across. During this interval, it still swims about in the infusion, darting its head among the surrounding particles of matter. The con traction gradually augments, and the animalcula is at length changed into two spherules, connected to each other only by a single point. Their motion is now fre quently interrupted, until at last complete separation takes place, and two perfect animals are produced. At
first they appear unable to move; but each resumes the velocity of the original whole, and in a short time ac quires its full size. Sometimes the rapidity of their motion is not realized; and, during the progress of di vision, the size of each part becomes nearly as great as that of the entire animal.
That naturalists may be enabled to repeat these cu rious experiments, it is fit, that, before further illus tration of the subject, we should explain the method of isolating an invisible animal. A drop of infusion is conveyed into a watch glass, with the point of a pen, it is of no consequence though abounding with animal cula, and a drop of water put two or three lines distant from it. A channel is then made between them, by drawing out the circumference of the drops. The ani malcula are not slow in finding the channel, which they traverse, and arrive one after another in the drop of water. Whenever an animalcula is observed with a magnifier to enter the drop, the communication of the channel is cut off with a hair pencil, and the single ani malcula imprisoned.
But to return. There is a species of animalcula form ed in infusions of hemp-seed, which is described by M. Bonnet, as provided with a beak, or hook, at the ante rior part. When an animalcula is about to divide, it seeks a convenient place at the bottom of its infusion, commonly among that semi-transparent kind of muci lage which is formed in those of hemp seed. After searching and examining various places, it at last fixes on one. The body, which is naturally long, contracts ; the curved beak is retracted or concealed, and the ani mal assumes a spherical figure. It next begins to re volve on itself, so that the centre of motion is fixed, or the sphere never changes its place. The motion is per formed with the most perfect regularity, but the direc tion of rotation is constantly changing, in such a man ner that the rotation may be first from right to left, then from before, and next from left to right, and all these changes are perfectly performed, without the animal cola, or rotatory machine, changing its place. At length the motion accelerates, and at the point where the sphere seemed motionless, two cross divisions begin to be visible, exactly like the husk of a chesnut ready to burst. In a little longer, theanimal appears agitated, and making great exertions, and at last divides into four parts, the same as the producing animalcula, but smaller. These grow larger, and each divides into four, which in their turn encrease, and the young al ways become equal to the parent, if the word parent may be used in this singular mode of generation.