58 DISTRIBUTION OF ANIMALS. [part i. 



maintained. For they will find, that a careful consideration of 

 the exceptional means of dispersal and conditions of existence of 

 each group, will explain most of the divergences from the normal 

 distribution of higher animals. 



We shall thus be led to an intelligent comprehension of the 

 phenomena of distribution in all groups, which would not be 

 the case if every specialist formed regions for his own particular 

 study. In many cases we should find that no satisfactory 

 division of the earth could be made to correspond with the dis- 

 tribution even of an entire class ; but we should have the cole- 

 op terist and the lepidopterist each with his own Geography. Aud 

 even this would probably not suffice, for it is very doubtful if 

 the detailed distribution of the Longicornes, so closely dependent 

 on woody vegetation, could be made to agree with that of the 

 Staphylinidre or the Carabidse which abound in many of the 

 most barren regions, or with that of the Scarabeidae, largely de- 

 pendent on the presence of herbivorous mammalia. And when 

 each of these enquirers had settled a division of the earth into 

 "regions" which exhibited with tolerable accuracy the pheno- 

 mena of distribution of his own group, we should have gained 

 nothing whatever but a very complex mode of exhibiting 

 the bare facts of distribution. We should then have to begin 

 to work out the causes of the divergence of one group from 

 another in this respect ; but as each worker would refer to his 

 own set of regions as the type, the whole subject would become 

 involved in inextricable confusion. These considerations seem 

 to make it imperative that one set of " regions " should be 

 established as typical for Zoology ; and it is hoped the reasons 

 here advanced will satisfy most naturalists that these regions 

 can be best determined, in the first place, by a study of the dis- 

 tribution of the mammalia, supplemented in doubtful cases by 

 that of the other vertebrates. We will now proceed to a discus- 

 sion of what these regions are. 



Various Zoological Regions proposed since 1857. — It has already 

 been pointed out that a very large number of birds are limited 

 by the same kind of barriers as mammalia ; it will therefore 

 not be surprising that a system of regions formed to suit the 



