38 ON THE STUDY OF ZOOGEOGRAPHICAL REGIONS, 



The composition of a Regional Fauna. 



One of the great advantages of the method of Specific Contours 

 is that it clearly separates out the different types or "layers," as 

 it were, which make up the fauna of any given region. The 

 attempts to subdivide regions into definite subregions do not give 

 sufficient prominence to this, but tend rather to give an idea of 

 essential differences between the divisions, separated by hard and 

 fast lines. The method of Specific Contours may be called a 

 three-colour process, in which the true " colour " or appearance of 

 any given fauna is obtained by the superposition of separate 

 plates on which the three different distributions, ectogenic, ento- 

 genic, and palseogenic, are drawn. Only by such an analytical 

 process can we obtain a clear idea of the changes in the faunal 

 character of different parts of a region. 



To take a good example of this :— The North Queensland coast- 

 line does not strike the visitor as typically Australian in either 

 its fauna or flora. Yet if these be analysed, the very strong 

 entogenic element very soon becomes apparent, and the overlying 

 ectogenic element which marks it can be differentiated out as of 

 Oriental origin. As soon as one gets inland, the effect of the 

 ectogenic element becomes much less marked, and the entogenic 

 fauna and flora show up very distinctly. As one travels south- 

 wards, the effect of the ectogenic element diminishes. 



Again, on the Blue Mountains, there is at once apparent a 

 very strongly marked entogenic fauna and flora. Almost lost in 

 this, but still present — and, by its presence, adding to the variety 

 and interest of the fauna — we distinguish the remains of palseo- 

 genic groups whose value to the phylogenist can scarcely be over- 

 estimated. 



The factors oj zoogeoy raphical distribution. 



Different students of zoogeography have given prominence to 

 various factors which have brought about the present distribu- 

 tion of the fauna and flora of the earth. It is necessary, how- 

 ever, to distinguish clearly between the two classes of factors 

 which contribute to the result. They may be classed as follows : 



i. Primary Factors. — Those which determine the presence or 

 absence of groups in the fauna or flora of a region. These factors 



