IV. INTRODUCTION. 
that organic distribution depends on soil and climate; for we often find a perfect identity 
of these conditions in opposite hemispheres and in remote continents, whose faune and 
floree are almost wholly diverse. It does zo¢ imply that allied but distinct organisms 
have been educed by generation or spontaneous development from the same original stock ; 
for (to pass over other objections) we find detached volcanic islets which have been ejected 
from beneath the ocean, (such as the Galapagos for instance,) inhabited by terrestrial forms 
allied to those of the nearest continent, though hundreds of miles distant, and evidently 
never connected with them. But this fact may indicate that the Creator in forming new 
organisms to discharge the functions required from time to time by the ever vacillating 
balance of Nature, has thought fit to preserve the regularity of the System by modifying 
the types of structure already established in the adjacent localities, rather than to proceed 
per saltum by introducing forms of more foreign aspect. We need not, however, pursue 
this enquiry further into obscurity, but will merely refer to the law of geographical distri- 
bution, as bearing on the subject before us. 
In the Indian Ocean, to the east of Madagascar, are three small volcanic islands, which, 
though somewhat scattered, are nearer to each other than to any neighbouring land. This 
circumstance gives them a claim to be regarded as a geographical group, a meagre fragment 
of an archipelago, although in a general sense they are connected with Madagascar, and 
more remotely with the African continent. In conformity with the above-mentioned relation 
between geographical distribution and organic structure, we find that a small portion of 
the indigenous animals and plants of those islands are either allied or identical with the 
products of Africa, a larger portion with those of Madagascar, while certain species are 
peculiar to the islands themselves. And as these three islands form a detached cluster, as 
compared to other lands, so do we find in them a peculiar group of birds, specifically different 
in each island, yet allied together in their general characters, and remarkably isolated from 
any known forms in other parts of the world. ' These birds were of large size and grotesque 
proportions, the wings too short and feeble for flight, the plumage loose and decomposed, 
and the general aspect suggestive of gigantic immaturity. The history of these birds was 
as remarkable as their organization. About two centuries ago their native isles were first 
colonized by Man, by whom these strange creatures were speedily exterminated. So rapid 
and so complete was their extinction that the vague descriptions given of them by early 
navigators were long regarded as fabulous or exaggerated, and these birds, almost 
