1902.] AND ANCIENT GEOGKAPHY. 271 



that any research in this direction is deemed incomplete that is not 

 finished by the creation or discussion of " regions." 



In opposition to this, we wish to emphasize that we consider it 

 entirely a matter of indifference whether we accept any regions or 

 not, since none of the possible schemes can be satisfactory. Only 

 in a very limited degree and in a modified sense we believe it ad- 

 visable to divide the earth into regions, and we have proposed such 

 a division for the marine life districts. 1 This scheme, however, is 

 not intended to represent or to express the actual distribution of 

 any animals, but it is a scheme of the distribution of the conditions 

 of existence in the oceans of the present time without consideration 

 of the past or of any definite group of animals. The only purpose 

 of these regions is to single out those marine animals which corre- 

 spond to the normal conditions of life and to separate them from 

 the abnormal cases ; under " normally distributed" consequently, we 

 mean those animals which shape their distribution according to the 

 present features of the earth's surface and which belong in their 

 origin to recent time. All the rest differs and does not fit into 

 these regions ; but instead of leaving them out of consideration we 

 know that just these cases are the most interesting, since they 

 demand closer investigation. In most cases we find that these in- 

 stances of "abnormal " distribution are to be traced back into the 

 geological past in order to be properly understood. This latter 

 study is the most important branch of Zoogeography, and we see 

 that the introduction of "regions" in our method is only the 

 means by which we discover the more interesting and important 

 cases, but it is not the final aim. 



Of course the same method may also be used for land and fresh- 

 water animals, and it may here be incidentally remarked that the 

 regions proposed by Wallace are in this respect superior to any 

 modifications introduced by later authors, since they generally are 

 well limited and isolated by physical boundaries given on the sur- 

 face of the earth. But if we are satisfied with the simple statement 

 of the fact that some animals fit into these regions while others do 

 not, we do not approach the solution of the question as to how the 

 actual distribution originated : we are to advance one step further 

 and investigate those cases which do not submit to the scheme. 

 The final aim of this investigation is to compare and group together 



1 Ortmann, A. E., Grundzuege der marinen Thiergeographie, Jena, 1896. 



