ISLAND LIFE 



never now be obtained owing to the reckless destruction of 

 forests and with them of countless species of plants and 

 animals. In the next place we require a true and natural 

 classification of animals and plants, so that we may know 

 their real affinities ; and it is only now that this is being 

 generally arrived at. We further have to make use of the 

 theory of *' descent with modification '' as the only possible 

 key to the interpretation of the facts of distribution, and 

 this theory has only been generally accepted within the 

 last twenty years. It is evident that, so long as the belief 

 in "special creations" of each species prevailed, no explan- 

 ation of the complex facts of distribution could be arrived 

 at or even conceived ; for if each species was created where 

 it is now found no further inquiry can take us beyond 

 that fact, and there is an end of the whole matter. An- 

 other important factor in our interpretation of the phe- 

 nomena of distribution, is a knowledge of the extinct forms 

 that have inhabited each country during the tertiary and 

 secondary periods of geology. New facts of this kind are 

 daily coming to light, but except as regards Europe, North 

 America, and parts of India, they are extremely scanty ; 

 and even in the best-known countries the record itself is 

 often very defective and fragmentary. Yet we have al- 

 ready obtained remarkable evidence of the migrations of 

 many animals and plants in past ages, throwing an often 

 unexpected light on the actual distribution of many 

 groups.^ By this means alone can we obtain positive 

 evidence of the past migrations of organisms ; and when, 

 as too frequently is the case, this is altogether wanting, we 



European governments. Such are the Sandwich Islands, Tahiti, the 

 Marquesas, the Philippine Islands, and a host of smaller ones ; while 

 Bourbon and Mauritius, St. Helena, and several others, have only been 

 adequately explored after an important portion of their productions has 

 been destroyed by cultivation or the reckless introduction of goats and 

 pigs. The employment in each of our possessions, and those of other 

 European powers, of a resident naturalist at a very small annual expense, 

 would have done more for the advancement of knowledge in this direction 

 than all the expensive expeditions that have again and again circumnavi- 

 gated the globe. 



^ The general facts of Paleontology, as bearing on the migrations of 

 animal groups, are summarised in my Geographical Distribution of Aiiimals^ 

 Vol. I. Chapters VI., YIL, and YIII. 



