INTRODUCTION. 7 



modelled upon tliat of the adult, and wliera the scale of ideas is limited, 

 they must be as essentially hereditary as the external form.'" x\n English 

 writer endeavors to found a distinction between instinct and reason, by 

 citing the case of a young animal, as a monkey, being terrified by one of 

 it^ natural enemies, as a large serpent, when seen for the first time, which 

 would not be. the case with a young human being. Nevertheless, if man 

 were for ages subject to be devoured by a large reptile, watching and 

 caution would at length become habitual, and be transmitted as an instinct. 

 The brain of the young is not necessarily that of the adult, but that of the 

 adult at an earlier stage. So a quality or habit is not always transmissible 

 from a parent to its innnediate offspring, but it may appear in a more 

 distant descendant, by a kind of " alternation of generations." Cdonel 

 Hamilton Smith considers tlie spotted horse as an original Asiatic race 

 with which the ordinary breeds were sometimes crossed, and he thus 

 accounts for the occasional appearance of examples of it. The original 

 race is mild and intelligent, which is one reason for its frequent use in 

 equestrian exhibitions. 



One of the most important inquiries in the history of animals and plants, 

 is that which relates to their distribution. That of the latter has been 

 treated of under Botany ; and as regards animals, our contracted space 

 limits us to the following general view. 



There are both aquatic and terrestrial animals, the number of which may 

 perhaps be equal ; but there are also species which can live both in water 

 and on land, as many of the amphibia, and some other vertebrata. Some 

 aquatic animals live partly in fresh, and some in salt water ; but there are 

 others which leave the sea to spawn in the fresh water, as the salmon. 

 In the sea itself there are several regions depending upon the depth. Some 

 marine animals live near or at the surface, others upon the bottom, in some 

 cases within certain limits as to depth. Many land and sea animals live 

 only as parasites upon or within others. Some species have a peculiar 

 parasite, while others support several kinds. 



Zoogeography, or the geographical distribution of animals, teaches the 

 circumstances and positions under which animals occur, both as regards 

 individual species, genera, or larger groups. The chief circumstances 

 which seem to control animal distribution, are temperature, elevation, and 

 natural barriers ; whence it results that not only the continents, but much 

 smaller regions, have their peculiar founa. In proceeding from the tropics, 

 species will be found to diminish rapidly. Some animals are circumscribed 

 within very narrow limits, being confined to a single locality, as the curious 

 reptile genus Amblyrhynchus to the Galapagos islands, or the Aurochs 

 (Bison priscus) to a single forest in Russia. The genus Bradypus (sloth) 

 and Dasypus (armadillo), Auchenia (llama), are confined to South America ; 

 the Marsupialia (possum, &c.) to America and Australia, and the Zebras to 

 Africa. Others are more widely spread, as the dogs, bats, mice, &c. 



* These views are favorable to the doctrine of innate ideas, which is generally opposed by 

 speculative reasoners. 



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