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Show 412 CLASSIFICATION. CHAP. XIII. spec.i· e s. c on sequently the groups whidc h a.r e now larg. e, d h. 1 generally include many ominant species, an w IC 1 . · If 1 tend to go on increasing indefinitely 1? size. urt 1er tt t d to show that from the varying descendants of a emp e d d'.Cl' each species trying to occupy as many an as Iue~ent 1 as possible in the economy of nature, there IS a p aces d. 'rhi c,o ns tant tendency in their chara.c ters tlo Iv erged.' . s conclusion was supported by looking at t 1e great IVer~Ity f the forms of life which, in any small area, come mto ~he closest competition, and by looking to certain facts in naturalisation. I attempted also to show that. there. is ~ constant tendency in the .forms which are mcreasmg In nu~ber and diverging in character, to supplant aud extermin~te the less divergent, the less improved, and pre.cecling forms. I request the reader to turn to. the diagram illustrating the action, as formerly explained,. of .these several principles ; and he will see that the I~evitable result is that the modified descendants proceeding fro~ one progenitor become broken up into groups suborchnate to groups. In the diagram eac~ let~er on the uppermost line may represent a genus uwluding several species ; and all the genera on this line form toge~her one class, for all have descended from one. anc~ent but unseen parent, and, consequently, have Inhented something in common. But the throe ge~era on the left hand have on this same principle, much In common, and form a sub-family, distinct from that including the next two genera on the right hand, which diverged from a common parent at the fifth stage of descent. These 1 · mon· five genera have also much, though ess, In ?om . '. and they form a family distinct from that Includi?g the three genera still further to the right hand, wlnch diverged at a still earlier period. And all these geneih·a, d d. t' t from t e descended from (A), form an or er IS Inc CHAP. XIII. CLASSIFICATION. 413 gene.r a descended from (I) ·. So that we her·e h ave many speCies .descended from a SI~1gle progenitor grouped into genera , and the genera are Included in, or subordinat t su b- fa: mi'1 I' es, f:a mi'1i'e s, ~nd orders, all united into one clea sos., Th~s, the grand fact In natural history of the subordi .. nation of group under. group, v~hich, from its famiHarity, does not al:Vays sufficiently stnke us, is in my judgment fully explmned. N_ a~ura.lists try to arrange the species, genera, and families In each class, on what is called the Natural System. But what is meant by this system ? Some authors look ~t. it me~ely as ~ scheme for arranging together those hYing obJeets whiCh are n1ost alike and for separating those which are Inost unlike; or as an 'artificial me~~s for enunc~ating, as briefly as possible, general proposJtwns,- that Is, by one sentence to give the characters common, for instance, to all mammals, by another those common to all carnivora, by another those com_ mon to the dog-genus, and then by adding a single sentenc~, a ful~ descript~~n is gi~en of each kind of dog. The Ingenuity an~ utih~y of tlus system are indisputable. But n1any naturalists think that smnething more is meant by the Natural System ; they believe that it reveals the plan o.f t~e Creator; but unless it be specified whether order In time oi: space, or what else is meant by the plan of the Creator, It seems to me that nothing is thus added to o~r knowledge. Such expressions as that famous one of L1nnreus, and which we often meet with in a more or less concealed form, that the characters do not make the ?enus, but that the genus gives the characters, seem to l~ply that something more is included in our classificatwn, t~a.n mere resemblance. I believe that something more I8 Included; and that propinquity of descent,-the ?nly known cause of the similarity of organic beingsI8 the bond, hidden as it is by various degrees of modifi- |