In a similar manner, the Crocodile in the Llanos of Venezuela, the land and water Tortoises on the Orinoco, and the colossal Boa, and many of the smaller species of serpents, lie torpid and motionless in the hardened ground, throughout the hot and dry season of the year. The missionary Gilij relates, that the natives, in seeking the dormant Terekai (land-tortoises), which lie buried in dry mud to the depth of 16 or 17 inches, are often bitten by serpents suddenly awakened, and which had buried themselves with the tortoises. An admirable observer, Dr. Peters, who has only just returned from the eastern coast of Africa, writes to me as follows: “I could not obtain any certain information regarding the Tenrec during my short stay in Madagascar, but I am, on the other hand, well aware, that in the portion of eastern Africa where I spent several years, different species of tortoises (Pentonyx and Trionices) remain enclosed for months together, without food, in the parched and indurated ground, during the dry season of this tropical country. The _Lepidosiren_ also remains motionless and coiled up in the hardened earth, from May to December, wherever the swamps have been dried up.” We thus meet with an enfeeblement of certain vital functions in numerous and very different classes of animals, and, what is peculiarly striking, without the same phenomenon presenting itself in organisms nearly allied, and belonging to one and the same family. The northern glutton (Gulo), allied to the badger (Meles), does not, like the latter, sleep during the winter; whilst, according to Cuvier, “a Myoxus (Dormouse of Senegal, Myoxus Coupeii) which had probably never experienced a winter-sleep in its tropical home, fell into a state of hybernation at the beginning of winter, the first year it was brought to Europe.” This enfeeblement of the vital functions and vital activity passes through several gradations, according as it extends to the processes of nutrition, respiration and muscular movement, or induces a depression of the cerebral and nervous systems. The winter-sleep of the solitary bear and of the badger is not attended with rigidity, and hence the awakening of these animals is easy, and, as I frequently heard in Siberia, very dangerous to the hunters and country people. The recognition of the gradation and connection of these phenomena leads us to the so-called _vita minima_ of the microscopic organisms, which occasionally fall in the Atlantic in showers of meteoric dust, and some of which have green ovaries and are engaged in a self-generating process. The apparent revivification of the Rotifera and of the siliceous-shelled Infusoria is only the renewal of long enfeebled vital functions—a condition of vitality never entirely extinguished, but merely revived by excitation. Physiological phenomena can only be comprehended by being traced