In the hot and dry season, the crocodile in the Llanos of Venezuela, the land and water tortoises of the Orinoco, the huge boa, and several smaller kinds of serpents, become torpid and motionless, and lie incrusted in the indurated soil. The missionary Gili relates that the natives, in seeking for the slumbering Terekai (land tortoises), which they find lying at a depth of sixteen or seventeen inches in dried mud, are sometimes bitten by serpents which become suddenly aroused, and which had buried themselves at the same time as the tortoise. An excellent observer, Dr. Peters, who has just returned from the East Coast of Africa, writes thus to me on the subject:--“During my short stay at Madagascar I could obtain no certain information respecting the Tenrec; but, on the other hand, I know that in the East of Africa, where I lived for several years, different kinds of tortoises (Pentonyx and Trionchydias) pass months during the dry season of this tropical country inclosed in the dry hard earth, and without food. The Lepidosiren also, in places where the swamps are dried up, remains coiled up and motionless, encased in indurated earth, from May to December.” Thus we find an annual enfeeblement of certain vital functions in many and very different classes of animals, and, what is particularly striking, without the same phenomena being presented by other living creatures nearly allied to them, and belonging to the same family. The northern glutton (Gulo), though allied to the badger (Meles), does not like him sleep during the winter; whereas, according to Cuvier’s remark, “a Myoxus (dormouse) of Senegal (Myoxus coupeii), which could never have known winter-sleep in his tropical home, being brought to Europe fell asleep the first year on the setting in of winter.” This torpidity or enfeeblement of the vital functions and vital activity passes through several gradations, according as it extends to the processes of nutrition, respiration, and muscular motion, or to depression of the activity of the brain and nervous system. The winter-sleep of the solitary bears and of the badger is not accompanied by any rigidity, and hence the reawakening of these animals is so easy, and, as was often related to me in Siberia, so dangerous to the hunters and country people. The first recognition of the gradation and connection of these phenomena leads us up to what has been called the “vita minima” of the microscopic organisms, which, occasionally with green ovaries and undergoing the process of spontaneous division, fall from the clouds in the Atlantic sand-rain. The apparent revivification of rotiferæ, as well as of the siliceous-shelled infusoria, is only the renewal of long-enfeebled vital functions,--a state of vitality which was never entirely extinct, and which is fanned into a fresh flame, or excited anew, by the appropriate stimulus. Physiological phenomena can only be comprehended by being traced throughout the entire series of analogous modifications.