described in the following manner: HYDRA.[111] Flos: os terminale, cinctum cirris setaceis. Stirps vaga, gelatinosa, uniflora, basi se affigens.[112] [108] Philosophical Transactions. [109] Micrographia Illustrata. [110] Natural History of the Polype. [111] The hydræ or polypes have generally been denominated Insects: is there not a manifest impropriety in the application of this term to them? If we admit of the systematic arrangement of LINNÆUS, we find that he has divided the animal kingdom into six classes: 1. Mammalia. 2. Aves. 3. Amphibia. 4. Pisces. 5. _Insecta_; and 6. _Vermes_. Of the last or _Vermes_, the Zoophytes (from ζωοφυτον, or animal plant) constitute the fifth order. He defines it as Animalia composita, efflorescentia more vegetabilium: amongst these he includes the various species of Vorticellæ and Hydræ. The term animalculæ, or small animals, is certainly not inapplicable to them, but they differ materially in the peculiar characteristics by which insects are distinguished, see page 179, and pages 215-220. They do not undergo those transformations to which insects are subject, and which have been so fully described in the preceding part of this work: their figure, habits, and œconomy are also very different. In short, they seem to be in every respect, except their minuteness, quite a distinct race of animated beings, as will be more fully exemplified in the following pages. EDIT. [112] Lin. Syst. Nat. p. 1320. This animal fixes itself by its base, it is gelatinous, linear, naked, can contract itself, and change its place. Its mouth, which is at one end, is surrounded by hair, like feelers. It sends forth its young ones from its sides, which drop off. 1. Hydra viridis, tentaculis subdenis brevioribus. Green polype, generally with about ten short arms; it is represented in Plate XXI. Fig. 5. 2. Hydra fusca, tentaculis suboctonis longissimis. This polype has very long arms, often eight in number; it is represented at Plate XXI. Fig. 7. The arms are several times longer than the body. 3. Hydra grisea, tentaculis subseptenis longioribus. This polype has also generally long arms, in number about seven; it is of a yellowish colour, small towards the bottom; it is represented at Plate XXI. Fig. 6. 4. Hydra pallens, tentaculis subsenis mediocribus. The arms of this polype are generally about six in number, and of a moderate length. 5. Hydra hydatula, tentaculis quaternis obsoletis corpore vesicario. Plate XXI. Fig. 1, 2, 3, 4. This polype has a vesicular body, and four obsolete arms; is found in the abdomen of sheep, swine, &c. 6. Hydra stentorea, tentaculis ciliaribus corpore infundibuliformi. This polype has been called tunnel-shaped; the mouth is surrounded with a row of hairs; it is represented at Plate XXII. Fig. 27 and 28. 7. Hydra socialis, mutica torosa rugosa. Bearded, thick, and wrinkled. Plate XXI. Fig. 11.