CHAP. XVIII.] 
BIRDS. 
335 
Zealand, Tristan d’Acunha, and other oceanic islands ; and the 
phenomenon is clearly dependent on the long-continued absence 
of enemies, which allowed of great increase of bulk and the 
total loss of the power of flight, without injury. In some few 
cases (the Ostrich for example) birds incapable of flight co-exist 
with large carnivorous mammalia ; but these birds are large and 
powerful, as well as very swift, and are thus able to escape from 
some enemies and defend themselves against others. The entire 
absence of the smaller and more defenceless ground-buds from 
the adjacent island of Madagascar, is quite in accordance with 
this view, because that island has several small but destructive 
carnivorous animals. 
General Remarks on the Distribution of the Columbce. 
The striking preponderance of Pigeons, both as to genera and 
species, in the Australian region, would seem to indicate that at 
some former period it possessed a more extensive land area in 
which this form of bird-life took its rise. But there are other 
considerations which throw doubt upon this view. The western 
half of the Malay Archipelago, belonging to the Oriental region, 
is also rich in pigeons, since it has 43 species belonging to 11 
genera, rather more than are found in all the rest of the Oriental 
region. Again, we find that the Mascarene Islands and the An- 
tilles both possess more pigeons than we should expect, in pro- 
portion to those of the regions to which they belong, and 
to their total amount of bird-life. This looks as if islands were 
more favourable to pigeon-development than continents ; and if 
we group together the Pacific and the Malayan Islands, the 
Mascarene group and the Antilles, we find that they contain to- 
gether about 170 species of pigeons belonging to 24 out of the 47 
genera here adopted ; while all the great continents united only 
produce about the same number of species belonging (if we omit 
those peculiar to Australia) to only 20 genera, The great deve- 
lopment of the group in the Australian region may, therefore, be 
due to its consisting mainly of islands, and not to the order 
having originated there, and thus having had a longer period in 
which to develop. I have elsewhere suggested (Ibis 1865, p. 366) 
