CHAP. XXIII.] 
SUMMARY AND CONCLUSION. 
553 
forms and their habitats, are entirely nnnoticed, 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 still 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. 
