xxix] LITERARY WORK, ETC., 1871-1886 99 



humming birds, as illustrating the luxuriance of tropical 

 nature ; and others on the colours of animals and of plants, 

 and on various biological problems. 



As soon as we were settled at Croydon, I began to work 

 at a volume which had been suggested to me by the neces- 

 sary limitations of my "Geographical Distribution of Animals." 

 In that work I had, in the first place, dealt with the larger 

 groups, coming down to families and genera, but taking no 

 account of the various problems raised by the distribution 

 of particular species. In the next place, I had taken little 

 account of the various islands of the globe, except as forming 

 subregions or parts of subregions. But I had long seen the 

 great interest and importance of these, and especially of 

 Darwin's great discovery of the two classes into which they 

 are naturally divided — oceanic and continental islands. I 

 had already given lectures on this subject, and had become 

 aware of the great interest attaching to them, and the great 

 light they threw upon the means of dispersal of animals and 

 plants, as well as upon the past changes, both physical and 

 biological, of the earth's surface. In the third place, the 

 means of dispersal and colonization of animals is so con- 

 nected with, and often dependent on, that of plants, that a 

 consideration of the latter is essential to any broad views as 

 to the distribution of life upon the earth, while they throw 

 unexpected light upon those exceptional means of dispersal 

 which, because they are exceptional, are often of paramount 

 importance in leading to the production of new species and 

 in thus determining the nature of insular floras and faunas. 



Having no knowledge of scientific botany, it needed some 

 courage, or, as some may think, presumption, to deal with 

 this aspect of the problem ; but, on the other hand, I had 

 long been excessively fond of plants, and was always in- 

 terested in their distribution. The subject, too, was easier 

 to deal with, on account of the much more complete know- 

 ledge of the detailed distribution of plants than of animals, 

 and also because their classification was in a more advanced 

 and stable condition. Again, some of the most interesting 



