408 
ISLAND LIFE. 
[part II. 
reached the group by means of intervening islands afterwards 
submerged, and to have thenceforth remained to increase and 
multiply unchecked by the attacks of any more powerful 
animals, we can well understand that the wings, being useless, 
would in time become almost aborted . 1 It is also not im- 
probable that this process would be aided by natural selection, 
because the use of wings might be absolutely prejudicial to the 
birds in their new home. Those that flew up into trees to roost, 
or tried to cross over the mouths of rivers, might be blown out 
to sea and destroyed, especially during the hurricanes which 
have probably always more or less devastated the islands ; while 
on the other hand the more bulky and short-winged individuals, 
who took to sleeping on the ground in the forest, would be pre- 
served from such dangers, and perhaps also from the attacks of 
birds of prey which may always have visited the islands. But 
whether or no this was the mode by which these singular birds 
acquired their actual form and structure, it is perfectly certain 
that their existence and development depended on complete 
isolation and on freedom from the attacks of enemies. We 
have no single example of such defenceless birds having ever 
existed on a continent at any geological period, whereas analogous 
1 That the dodo is really an abortion from a more perfect type, and not a 
direct development from some lower form of wingless bird, is shown by its 
possessing a keeled sternum, though the keel is exceedingly reduced, being 
only three-quarters of an inch deep in a length of seven inches. The most 
terrestrial pigeon — the Didunculus of the Samoan islands, has a far deeper 
and better developed keel, showing that in the case of the dodo the 
degradation has been extreme. We have also analogous examples in other 
extinct birds of the same group of islands, such as the flightless Rails — 
Aphanapteryx of Mauritius and Erythromaclius of Rodriguez, as well as 
the large parrot — Lophopsittacus of Mauritius, and the Night Heron, 
Nycticorax megacephala of Rodriguez, the last two birds probably having 
been able to fly a little. The commencement of the same process is to be 
seen in the peculiar dove of the Seychelles, Turtur rostratus, which, as 
Mr. Edward Newton has shown, has much shorter wings than its close 
ally, T. picturatus, of Madagascar. For a full and interesting account of 
these and other recently extinct birds see Professor Newton’s article on 
“Fossil Birds” in the Encyclopaedia Britannica, ninth edition, vol. iii., 
p. 782 ; and that on “ The Extinct Birds of Rodriguez,” by Dr. A. 
Gunther and Mr. E. Newton, in the Royal Society’s volume on the Transit 
of Venus Expedition. 
