180 AFFINITIES AND GEOGRAPHICAL 



posed of the Mergansers and Ducks, which live in great part 

 upon animal matters, another comprising the Geese and 

 Swans, which are purely vegetable feeders, and a third em- 

 bracing the Gallinules and Coots, whose diet is mixed. 



The tendency of these animals, in consequence of their 

 tastes in aliment, was to advance along rivers and the shores 

 of lakes, to those adjacent low grounds where vegetable food, 

 worms, and insects, are to be found. They landed, we may 

 say, either upon sandy beaches or upon those low shores 

 which, in the early ages of the world, antecedent to a time of 

 cultivation, were wholly covered with marshes. On came 

 the tide of population behind ; it behoves them to spread 

 landward for subsistence. The consequence was a modifica- 

 tion of the hitherto natatorial forms of these birds to suit a 

 strolling life upon soft sands and in marshes. The webbing 

 of the toes shrunk, being no longer required for swimming ; 

 the toes were elongated, so as to give support upon a yielding 

 ground or bottom ; the tarsi were also lengthened, to raise 

 the body of the bird above the shallow water in which it 

 walked : at the same time, the animal acquired a greater 

 length of neck and of bill to enable it to feed in these waters. 

 Behold then the Wading Birds (Grallatores of Cuvier) ; 

 merely a transformation of their swimming progenitors ! 

 In some parts of the earth, however, the regions adjacent 

 to the sea were not marshes, but extensive sandy plains, 

 presenting means of subsistence somewhat scantier, but still 

 not to be overlooked. The consequence was a branch of the 

 swimmers, adapted by length and strength of limbs for that 

 rapid progression from one place to another which is required 

 by animals placed on extensive wastes. This branch com- 

 prises the Running Birds (Cur sores), the Ostrich in Africa, 

 the Emeu and Cassowary of Australia, the Rhea of Ame- 

 rica, the Apterix of New Zealand ; characterized by an 

 extinction of the hind toe, which is not needed in their 

 field of existence, and a reduction of the wings for the 

 same reason in a modified degree, with, however, an ap- 

 proximation to mammalian characters, in the hair-like ap- 



