CHAPTER I. 



THE GENERAL FACTS OF THE DISTRIBUTION OF ANIMALS. 



Introductory. 



THE entire world both land and sea supports every- 

 where animal life. The extreme cold of the arctic regions 

 is not too intense to permit of the existence of at least a 

 few forms of life, while the warmer regions of the globe 

 have everywhere an abundant fauna, which increases 

 towards the tropics ; it is even probable that the icebound 

 antarctic continent, if it could be explored, would be found 

 to possess some inhabitants. 



The most elementary knowledge of Zoology is sufficient 

 to enable us to see that, while terrestrial life is as 

 abundant as marine, the kinds of animals inhabiting these 

 diverse situations are different. We can distinguish in 

 fac,t between purely terrestrial and purely aquatic animals. 

 The latter group can be again divided into two great 

 classes, those which inhabit the sea and those which 

 inhabit the fresh waters of the land. There is however 

 no absolute break between these various groups. The 

 B. Z. 1 



