CHAP. XXIII.] SUMMARY AND CONCLUSION. 553 



forms and their habitats, are entirely unnoticed, owing to the 

 productions of the same locality never being associated in our 

 museums and collections. A few such relations have been 

 brought to light by modern scientific travellers, but many more 

 remain to be discovered ; and there is probably no fresher and 

 more productive field stiU unexplored in Natural History. Most 

 of these curious and suggestive relations are to be found in the 

 productions of islands, as compared with each other, or with the 

 continents of which they form appendages ; but these can never 

 be properly studied, or even discovered, unless they are visibly 

 grouped together. When the birds, the more conspicuous families 

 of insects, and the land-shells of islands, are kept together so as 

 to be readily compared with similar associations from the adja- 

 cent continents or other islands, it is believed that in almost every 

 case there will be found to be peculiarities of form or colour 

 running through widely different groups, and strictly indicative 

 of local or geographical influences. Some of these coincident 

 variations have been alluded to in various parts of this work, 

 but they have never been systematically investigated. They 

 constitute an unworked mine of wealth for the enterprising 

 explorer ; and they may not improbably lead to the discovery of 

 some of the hidden laws (supplementary to Natural Selection), 

 which seem to be required, in order to account for many of the 

 external characteristics of animals. 



In concluding his task, the author ventures to suggest, that 

 naturalists who are disposed to turn aside from the beaten track 

 of research, may find in the line of study here suggested a new 

 and interesting pursuit, not inferior in attractions to the lofty 

 heights of transcendental anatomy, or the bewildering mazes of 

 modern classification. And it is a study which will surely lead 

 them to an increased appreciation of the beauty and the harmony 

 of nature, and to a fuller comprehension of the complex relations 

 and mutual interdependence, which link together every animal 

 and vegetable form, with the ever-changing earth which supports 

 them, into one grand organic whole. 



