. L'histoire naturelle. Zoologie. ANIMALCULES. 721. Fig. 8.-Infusoria cilié. J'Paramcficium. B, Stentor. Le Infusorians ciliées sont classées en fonction de l'arrangement de leurs cils. Parfois ces couvrir toute la surface du corps, comme dans la pantoufle animalcule (Fig. 8, A), qui est très commun dans l'eau de bassin ou dans l'infusion de foin, et de mesures -^^} dans y d'un pouce de longueur. Dans ce protozoaire, la distinction entre la partie externe du corps et l'intérieur de la partie est très clair, et la bouche et le tube menant de il sont très évidents. Dans la "peau" extérieure un certain nombre

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. Natural history. Zoology. ANIMALCULES. 721. Fig. 8.—Ciliated Infusoria. A J Paramcficium. B, Stentor. The Ciliated Infusorians are classed according to the arrangement of their cilia. These sometimes cover the whole surface of the body, as in the Slipper animalcule (Fig. 8, A), which is very common in pond water or in infusions of hay, and measures from -^ to y}^ of an inch in length. In this Protozoan, the distinction between the outer part of the body and the inner granulated part is very clear, and the mouth and tube leading from it are very evident. In the outer "skin" a number of small oval bodies can be seen pointing out- wards. These, which are known as trichocysts, are minute bags contain- ing threads which can be shot out of them and are probably used as a defence against enemies. These structures recall the stinging threads of the Coelenterates, but are still more wonderful as the products of a single cell. In the next division of the Ciliated Infusorians, very fine cilia cover the surface of the body, while longer ones encircle the mouth. The Trumpet animalcules (Fig. 8, B), usually about Jg of an inch in length, are found moving about freely in the water or attached, either singly or in groups, to some submerged object by the narrowed end of the body. The lower part of the body is sometimes protected by a kind of sheath or case. The wide opening at the free end which surrounds the mouth is fringed with long and strong cilia. In order to multiply, these Trumpet animalcules divide into two, a new mouth and oral fringe forming on the parent animal before division. The Infusorians of the next division have smooth bodies, the cilia being usually confined to the region round the mouth ; in some cases, how- ever, a second band of cilia surrounds some other part of the body. Some of the attached Infusorians of this kind surround themselves with a slipper- shaped case of protoplasm, which helps to protect the soft part of the body, and can, when nec

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