22 ON THE STUDY OP ZOOGEOGRAPHICAL REGIONS, 



regions may be marked ojff very definitely in the case of certain 

 groups— as, for instance, in the case of the Mammalia and the 

 Passerine Birds, for which they were originally instituted — yet 

 in other cases the boundaries between them may be more or less 

 transgressed, or may even be non-existent for certain groups. 

 This is, of course, due to the fact that the barriers which mark off 

 the different regions may not always have been barriers in time 

 past, nor may they be complete barriers in time present. It can 

 be easily seen, for instance, that Wallace's line need not prove a 

 bar to the migration of strong-flying insects, nor need the arid 

 tract that somewhat vaguely separates the Nearctic from the 

 Neotropical Region be any bar to the progress of eremian forms 

 of animals or plants. 



It is no wonder, therefore, that much less agreement should be 

 found amongst the opinions of students when we come to con- 

 sider the question of subregions. Many schemes have been pro- 

 posed for the subdivision of the six main regions into subregions 

 of approximately co-ordinate value. Possibly the desire for uni- 

 formity and symmetry has been one of the underlying forces in 

 some of these attempts. One scheme, with a good deal to recom 

 mend it,* divides each main region into four subregions. Such 

 divisions cannot, however, be regarded as of co-ordinate value. 

 To take an example, the Australian region is subdivided into the 

 Australian proper (Australia and Tasmania), the Papuan, the 

 Polynesian, and New Zealand (with its allied islands). Of these. 

 New Zealand stands in a higher rank than the others, and is 

 claimed by many scientists to form actually a separate region. 

 On the other hand, the division does not recognise the claims of 

 the South-Western corner of Australia, which, to botanists at 

 any rate, will appear to be as distinct a subregion as could pos- 

 sibly be found; while, on the other hand, the so-called Polynesian 

 subregion is founded purely on negative characters, and is only 

 doubtfully to be included in the Australian region at all. 



The present paper is an attempt to approach the subject from 

 a different view-point. The desire to draw hard-and-fast divi- 

 sions exaggerates the actual boundaries reared by Nature at 

 * Text-Book of Zoogeography, F. E. Beddard. 



