174 GEOGRAPHY OF ANIMALS. 



globe, even the most desolate, which is not occasion- 

 ally visited by some of the feathered tribes and even 

 permanently inhabited by some of the smaller kinds 

 of insects ; but it is notorious that such portions, 

 thus scantily occupied, can form only a small pro- 

 portion in comparison with the remainder of the earth. 

 The comparative distribution of the different classes 

 of animals, modified as it is by the circumstances 

 which afford them food and protection, is somewhat 

 curious. In the first place, it may be stated that 

 not only are the lowest classes, the invertebrata, the 

 most numerous, but they are also the most exten- 

 sively dispersed ; they are found distributed through 

 the air of the northern and tempemte climates during 

 summer, and that of the Tropics during the whole 

 year; through the sea; the snow of the North Pole, 

 upon as well as in the earth, and the vegetables which 

 proceed from it ; rivers, lakes, plains, and mountains, 

 alike present some links of these lower tribes ; and 

 even the bodies of the higher orders are the abodes 

 of a few kinds, for a certain period of their existence. 

 Lastly, stagnant waters and infusions contain a mul- 

 titude of minute beings ; and it has even been affirmed 

 that certain fluids'* of animal bodies contain micro- 

 scopic animalculae. The higher classes — Vertebrata 

 — which do not Hke the former elude our enumera- 

 tion and investigation of their habits and retreats, 

 are scattered thinly towards the Poles, but regularly 

 augment towards the Equator. Some few are the 

 denizens of high mountains ; a few penetrate the 

 earth ; a great proportion inhabit the great deep ; 

 lakes and rivers ; and about an equal number peo- 

 ple the surface of the ground and its productions. 

 The comprehensive statement which we have made, 

 that the lower are more widely distributed than the 

 higher class, will not be found to apply, however, in 

 comparing the distribution of the divisions into which 

 these classes have been naturally separated ; because 

 in tracing these, from above downwards, it is observed 



* Spallanzani has clearly proved this* — Ed. 



