CH. II] NEARCTIC REGION. 95 



A closer resemblance between the Nearctic and the 

 Palsearctic regions than that which obtains between, say 

 the Neotropical and the Ethiopian, would be expected on 

 the theory of the polar origin of life. That there is a 

 close resemblance has also some relation to the great 

 similarity in climate and physical conditions between the 

 two regions. But the question now for consideration 

 is whether the similarity is such as to warrant the 

 inclusion of the two in one Holarctic realm, as is 

 contended by Dr Heilprin and Prof. Newton. Dr Wallace 

 decidedly thinks not ; and his reasons for this opposition 

 are set forth in a special paper devoted to the question 1 . 

 It appears from his tables that there are 43 genera of 

 Mammals which are found in the Palaearctic region but 

 not in the Nearctic. On the other hand 39 are peculiar 

 to the Nearctic; 31 are common to both regions. 

 These estimates, even when slightly edited, as will be 

 indicated immediately, leave a respectable balance of 

 forms peculiar to each region; doubtless the number of 

 forms is poor when compared with other regions ; but it 

 must be borne in mind that these two temperate regions 

 do not abound in Mammalian life as do the more tropical 

 parts of the earth's surface. Of the 39 genera peculiar 

 to the Nearctic region seven may be not unfairly deducted 

 in making a final estimate as being largely, if not to a 

 greater extent, Central or South American, i.e. Neo- 

 tropical, also. The peccary, for example, is an animal 

 which is rather characteristic of the Neotropical than the 

 Nearctic region. The most striking argument however 



1 Natural Science, June, 1894. 



