THE INTRODUCTION OF NEW SPECIES. 9 



was given by the admirable paper of the lamented 

 Mr. Strickland, published in the "Annals of Na- 

 tural History," in which he so clearly showed the 

 true synthetical method of discovering the Natural 

 System. 



Geographical Distribution of Organisms. 



If we now consider the geographical distribu- 

 tion of animals and plants upon the earth, we 

 shall find all the facts beautifully in accordance 

 with, and readily explained by, the present hypo- 

 thesis. A country having species, genera, and 

 whole families peculiar to it, will be the neces- 

 sary result of its having been isolated for a long 

 period, sufficient for many series of species to 

 have been created on the type of pre-existing 

 ones, which, as well as many of the earlier- 

 formed species, have become extinct, and thus 

 made the groups appear isolated. If in any case 

 the antitype had an extensive range, two or more 

 groups of species might have been formed, each 

 varying from it in a different manner, and thus 

 producing several representative or analogous groups. 

 The Sylviadas of Europe and the Sylvicolidse of 

 North America, the Heliconidae of South America 

 and the Euploeas of the East, the group of Tro- 

 gons inhabiting Asia, and that peculiar to South 

 America, are examples that may be accounted for 

 in this manner. 



Such phenomena as are exhibited by the Gala- 



