XI PALEONTOLOGY AND EVOLUTION 867 



it has been instructively discussed in the thought- 

 ful and ingenious work of Mr. Andrew Murray 

 " On the Geographical Distribution of Mammals." ^ 



I propose to lay before you, as briefly as I can, 

 the ideas to which a long consideration of the 

 subject has given rise in my mind. 



If the doctrine of evolution is sound, one of its 

 immediate consequences clearly is, that the present 

 distribution of life upon the globe is the product 

 of two factors, the one being the distribution 

 which obtained in the immediately preceding 

 epoch, and the other the character and the extent 

 of the changes which have taken place in physical 

 geography between the one epoch and the other ; 

 or, to put the matter in another way, the Fauna 

 and Flora of any given area, in any given epoch, 

 can consist only of such forms of life as are directly 

 descended from those which constituted the Fauna 

 and Flora of the same area in the immediately 

 preceding epoch, unless the physical geography 

 (under which I include climatal conditions) of 

 the area has been so altered as to give rise to 

 immigration of living forms from some other 

 area. 



The evolutionist, therefore, is bound to grapple 



^ The paper * ' On the Form and Distribution of the Land- 

 tracts during the Secondary and Tertiary Periods respectively ; 

 and on the Effect upon Animal Life M'hich great Changes m 

 Geograpliical Configuration have probably produced," by Mr. 

 Searles V. Wood, jun., which was published in th.Q Philosophical 

 Magazine, in 1862, was unknown to me when this Address 

 Was written. It is well worthy of the most careful study. 



