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Show -.. CHAP. Vl. 184 DIFFICULTIES ON THEORY. . 1 t l'ke a creeper; it often, seen climbing branches, a mos I l h d . like a shrike, kills small birds by blows .onh t le e~ ' and I have many times seen and heard It ammer~ng h d f th On a branch and thus brealnng t e see s o e yew ' . h 1 . 1 th t h In North America the black bear t em I re a nu a c . . . b IIearne swimmino- for hours with widely was seen y o . . tl thus Catching like a whale, Insects In the open mou 1, ' . . water. Even in so extreme a case as this, If the supply of insects were constant, and if better adapted competitors did not already exist in the country, I can see no difficulty in a race of bears being. re~dered~ by natural selection, more and more aquatic In th~Ir structure and habits, with larger and larger mouths, till a creature was produced as monstr?us. a~ a whale. . . As we sometimes see Individuals of a speCies following habits widely different from those both of their own species and of the other species of the same genus, we might expect, on my t!1eory: that such ~ndivid1:als would occasionally have given rise to new speCies, having anomalous habits, and with their structure either slightly or considerably modified from that of their proper type. And such instances do occur in nature. Can a Inore striking instance of adaptation be given than that of a woodpecker for climbing trees and for seizing insects in the chinks of the bark? Yet in North America there are woodpeckers which feed largely on fruit, and others with elongated wings which chase insects on the wing; and on the plains of La Plata, whore not a tree grows, there is a woodpecker, whieh in every essential part of its organisation, even in itA colouring, in the harsh tone of its voice, and undulatory fljght, told. me plainly of its close blood-relationship to our common species; yet it is a woodpecker which never climbs a tree! Petrels are the most aerial and oceanic of birds, yet in the quiet Sounds of Tierra del Fuego, the Puffinuria CHAP. VI. TRANSITIONAL HABITS. 185 b~r~rdi, ~n its general habits, in its astonishing power of diVI~g~ Its ~anner of swimming, and of flying when unwillingly It takes flight, would be mistaken by any one for an auk ?r grebe; nevertheless, it is essentially a petrel, but. with many parts of its organisation profoundly modified. On · the other hand, the acutest observer by examining the dead body of the water-ouzel w~uld never have suspected its sub-aquatic habits ; yet this .anomalous member of the strictly terrestrial thrush fa:nul! wholly subsists by diving,-grasping the stones With Its feet and using its wings under water. He who believes that each being has been created as we now see it, must occasionally have felt surprise when he has met with an animal having habits and structure not at all in agreement. What can be plainer than that t~e ':ebbed feet of ducks and geese are formed for swimming? yet there are upland geese with webbed feet which rarely or never go near the water ; and no one except Audubon has seen the frio-ate-bird which has all its four toes webbed, alight on th~ surfac~ of the sea. On the other hand, grebes and coots are eminently aquatic, although their toes are only bordered by membrane. What seems plainer than that the long toes of grallatores are formed for walkino- over swamps and floating plants, yet the water-hen is n~arly as aquatic _as t~e coot; and the landrail nearly as terrestrial as the quail or p~rtridge. . In such cases, and many others could be given, habits have changed without a corresponding change of structure. The webbed feet of the ~pland goose may be said to have become rudimentary I~ function, though not in structure. In the frigatebrrd, the deeply-scooped membrane between the toes shows that structure has begun to change. H~ who believes in separate and innumerable acts of creatwn will say, that in these cases it has pleased the |