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cally considered. Among the mammals of this country, 

 hibernation was best exemplified in the winter sleep of the 

 common hedgehog, and we got various conditions of hiberna- 

 tion until the habit was met with so slightly developed as in 

 the hare, which slept in a partially torpid condition only 

 during and after severe and cold snowstorms, in little cave- 

 like hollows in the snow. During perfect hibernation all the 

 vital functions were in abeyance. The temperature of the 

 bodies of hibernating animals being nearly the same as that 

 of the surrounding atmosphere, the whole winter sleep was 

 greatly affected by temperature. After treating of the hiber- 

 nation of many species of mammals, fishes, and reptiles, the 

 antithesis of hibernation, known as aestivation, or the retire- 

 ment in hot countries during great summer heat and long- 

 continued drought of large numbers of animals, with almost 

 identical appearances as in hibernation, was then described ; 

 and the case of an animal allied to the common hedgehog, 

 inhabiting Madagascar, that activated for three months 

 during the sub-tropical summer, in burrows, just as our small 

 spiny friend hibernated during the winter months in Europe. 

 Many tortoises, crocodiles, and serpents, also most land 

 mollusca in hot countries, were said to activate. During the 

 heat of tropical India, large numbers of fish were in the 

 habit of retiring under the mud of their native pools as 

 the water evaporated, and in that condition could remain 

 apparently for an indefinite period ; for ponds which had 

 been dry for several years were found crowded with fine fish 

 on water being again admitted, and softening the hard cake of 

 mud which enveloped them. Animals which had been brought 

 to Europe from the tropics, and which were in the habit of 

 activating at home, generally activated in the colder climate 

 at the proper season. This indicated that some other influ- 

 ence than cold or heat induced these periods of sleep, though 

 certain temperatures necessarily favoured the conditions. 

 Neither abnormal heat nor abnormal mildness would stop 

 hibernation or aestivation respectively in some animals which 

 were subject to their influences ; when the time came round for 

 the periodical rest, sleep they must. It did not appear to be 



