6 ZOOLOGY. 



six years ; chickens live from twenty to thirty years ; parrots, ravens, and 

 swans, from eighty to one hvmdred ; a goose lived to near one hundred ; 

 an ass thirty-six; and a horse sixty. The colossal mammalia may live 

 several centuries. 



8. Plants and animals are subject to hybernation, a phenomenon which 

 we find especially in the polar and temperate zones, partly on account of 

 the absence of the necessary heat, the deficiency of the means of subsistence, 

 but also on account of a peculiar organization. In this condition plants 

 lose their leaves and animals fall into a continued death-like sleep, concealed 

 in holes and caves. All the functions are limited to their minimum. In 

 hot regions w^e find a corresponding summer repose in animals and plants, 

 connected with the great heat and aridity of the season. Then many 

 tropical plants shed their leaves ; crocodiles lie in the mud apparently dead, 

 land shells close their aperture by a diaphragm ; and certain freshwater 

 species bury themselves at the bottom of ponds which become desiccated, 

 until the return of the rainy season calls them to renewed life. 



9. Plants, like animals, exhibit, under certain circnmstances, great 

 tenacity of life. Seeds of plants can preserve their germinating power for 

 a long time, that of beans lasting one hundred years or more. An onion 

 found' in the hand of an Egyptian mummy germinated after an interval of 

 not less than two thousand years, and the same thing happened with some 

 cereal grains. The eggs of infusoria seem to afford a parallel in the animal 

 kingdom. The examples cited of living toads found embedded in solid 

 stone have not been sufficiently well authenticated to be admitted as facts, 

 nor have the species thus said to be found ever been described or named. 



10. Plants and animals become degenerate, as in the case of cultivated 

 vegetaldes, which are sometimes quite unlike their original species. 



11. There are living plants and animals which are capable of giving 

 light in the dark, as some of the former which grow in subterranean 

 passages, certain roots, and the blossoms of certain orange-flowered plants. 

 Many animals, as the Medusas and fire-flies, emit a phosphorescent light ; 

 and it is well known that decaying animal and vegetable matter is luminous 

 under certain circumstances. 



But notwithstanding the various relations between plants and animals, 

 there are still essential differences which it is sufficient merely to allude to 

 here. The most essential distinction lies in the free will of the animal, and 

 the power to make use of it in voluntary motion ; and the presence of 

 nervous matter to convey sensation, A mouth, muscles, bones, and organs 

 of sense, are not present in any plant. Animal heat, electricity, and art, 

 have no parallel among vegetables. 



Instinct is peculiar to animals, like that of migration, defence, the 

 constructions of bees and wasps, the expeditions of war and to make slaves 

 which ants undertake, etc. Instinctive actions are not taught, although a 

 permanent habit may become an instinct. The young duck swims at once, 

 the young snapping turtle bites when taken from the egg, and a harmless 

 serpent without fang or rattle will vibrate its tail like a rattlesnake, 

 producing a similar sound among dry leaves. The brain of the young is 

 210 



