XXII] CELEBES, THE MOLUCCAS, ETC. 359 



North America ; yet there is nothing on the map or on the 

 face of the islands to mark their limits. The boundary line 

 passes between islands closer together than others belonging 

 to the same group. I believe the western part to be a 

 separated portion of continental Asia, while the eastern is a 

 fragmentary prolongation of a former west Pacific continent. 

 In mammalia and birds the distinction is marked by genera, 

 families, and even orders confined to one region ; in insects 

 by a number of genera, and little groups of peculiar species, 

 the families of insects having generally a very wide or 

 universal distribution." 



This letter proves that at this time I had not the least 

 idea of the nature of Darwin's proposed work nor of the 

 definite conclusions he had arrived at, nor had I myself any 

 expectation of a complete solution of the great problem to 

 which my paper was merely the prelude. Yet less than two 

 months later that solution flashed upon me, and to a large 

 extent marked out a different line of work from that which 

 I had up to this time anticipated. 



I finished the letter after my arrival at Ternate (January 

 25, 1858), and made the following observation : "If you go to 

 the Andes I think you will be disappointed, at least in the 

 number of species^ especially of Coleoptera. My experience 

 here is that the low grounds are mttch the most productive, 

 though the mountains generally produce a few striking and 

 brilliant species." This rather hasty generalization is, I am 

 inclined still to think, a correct one, at all events as regards 

 the individual collector. I doubt if there is any mountain 

 station in the world where so many species of butterflies 

 can be collected within a walk as at Para, or more beetles 

 than at my station in Borneo and Bates' at Ega. Yet it may 

 be the case that many areas of about a hundred miles square 

 in the Andes and in the Himalayas actually contain a larger 

 number of species than any similar area in the lowlands of 

 the Amazon or of Borneo. In other parts of this letter I 

 refer to the work I hoped to do myself in describing, cata- 

 loguing, and working out the distribution of my insects. I 

 had in fact been bitten by the passion for species and their 



