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Show 108 DARWINISM CHAP. mor~ vegetarian diet, eating seeds as wcJl as insects, a,nd f?cdmg on t~e gt'ouncl as well a,s among· trees. The delicate l1ttlc blue titmouse (Parus croruleus), with its very small hi)] feeds on the minutest insects and grubs which it extract~ from crevices of bark and from the buds of fruit-trees. The marsh titmouse, again (Pa.rus palustris), has received its name from th~ low and mar hy localities it frcqncnts j while the crest~d t1tm?u e (Pm:us CI'istatus) is a northern bird frequenting cspeci~ll;Y, pmc for.c. ts, on the seeds of which trees it parti<tlly feeds. Ihen, agam, our three ~oi?mon pipits- the trcc-pipiL (Anth:l.s.arborcns), the mc:tdow-pipit (Anthus pratcnsis),ancl the r?cl~-p1p1t or s?a-l::trk (Anthus .obscurus) have c:tch occnpiccl a dtstmct plac~ m. nn,ture to whiC~ they have become spccinJly a~aptecl, as md1catcd by the different form and size of tho hm~ toe and claw.in c:teh species. So, the stone-chat (Saxicoh rubiCola,), the whm-?hat (S .. ruhetra), and the wheat-car (S. a:ma~the). are . all slightly d1vergcnt forms of one type, wilh modrficati~ns m tJ~c shape of the wing, feet, a,nd bill adapting them to shghtly different moclos of life. The whin-chat is Lhc sma~lost, and frequo.nts furzy commons, fields, and Jowla ncl 8, feedmg on worms, msccts, ~ small molluscs and bcrric. · the stonc-ch~t is next in size, and is cspcciaJly' active and li~cly, fr?qucntmg heaths and npla,nds, and is a permanent r esident With us, the two other . pecios being migr;tnts j while the larger and more co;1spicnous wheat-car, besides feeding on g1:ubs, beetles.' etc., IS able to captnre flying insects on the wmg, somethmg after the manner of true flycatchers. These examples sufficicn tly indicate how divcro-encc of ch~racter ~as acted, and has led to tho adaptation of 1~m1 cro11s allied s~eCies, each to a more or less special mode of life, witl1 the varwty of food, of habits, and of enemies which nmst. ncce~sari~_r: accomJ?any such diversity. And when we oxtcn<l o~r mqmnes to higher groups we find tho same indications of divergence and special adaptation, often to a still more marked c~tcnt. ?-'hus we have the larger falcons, which prey upon lm·ds, while some. of the smaller species, like the hobhy (Falco subbuteo), hve largely on insects. The true falcons capture their prey in the air, while the hawks usually seize it on or ne~r the ground, feeding on hares, rabbits, squirrels, grouse, pigeons, and poultry. Kites and buzzards, on the v NATURAL SELECTION 109 other hand, seize their prey upon tho ground, and the former feed largely on reptiles and omtl as well as on birds a11d quadrupeds. Others have adopted fish as their chief foo<1, and the osprey snatches its prey from the water with as much facility as a gull or a petrel ; while the outh American caracaras (Polyborus) have adopted the h;thit. of vultures and live altogether on carrion. In every groat group there is tho same divergence of habits. There arc ground-pigeons, rockpigeons, and wood-pigeons,-secd-eating pigeons and fruiteating pigeons; there arc carrion-eating, insect-eating, and fruit-eating crows. Even kingfi hers arc, some aquatic, . orne terrestrial in their habits; some live on :fish, some on insects, some on reptiles. Lastly, among the primary divisions of birds we find a purely terrestrial group- tho Ratitrc, including the ostriches, cassowaries, etc. ; other great grours, including the ducks, cormorant , gulls, penguins, etc., are aquatic; while tho bulk of the Passerine birds arc aerial and arboreal. The same general facts ca,n be detected in all other classes of animals. In the mammalia, for example, we have in the common rat a fish-cater and flesh -cater as well as a grain-e::tter, which has no doubt helped to gi vc it the power of spreading over the world and driving away tho native mts of other countric .. Throughout the Hodcnt tribe we find everywhere aquatic, terrestrial, and arboreal forms. In the weasel and cat tribes some live more in tree , others on the ground ; squirrels have diverged into terrestrial, arboreal, and flying species; and :finally, in the bats we have a truly aerial, a,nd in the whale. a truly aquatic order of mammals. We thus · sec that, beginning with different varieties of the same specie , we have allied species, genera, families, and orders, with similarly dive'rgcnt habits, and adaptations to different mod s of lif , indicating some general principle in natnrc which has been operative in tho development of the organic world. Bnt in order to be thus operative it mnst be a o·cncrally useful principle, and Mr. Darwin has very clearly shown us in what this utility consists. Divergence leads to a Maximum of Organic Forms in each A1·ea. Divergence of character has a double purpose and nse. In the first place it enables a species which is being overcome |