OCR Text |
Show 134 MACLEA 1f SYSTEM OJ' phically detached, these linfCi perhaps consisting of par· ticular typical groups placed in an independent successwn, o1· of two or more of these groups. And for this idea there is, even in the present imperfect state of our knowledge of animated nature, some countenance in ascertainerl facts, the birds of Australia, for example, being chiefly of the suctorial type, while it .1nay be presumed tha~ the <~bservation as to the predominance of the useful antmals 1n the Old World, is not 1nuch different from saying that the rasOl ·ial type is there peculiarly abundant. It does not appear that the idea of independent lines, consisting of particular types, or sets of types, is necessarily inconsistent with the general hypothesis, as nothing yet ascertained of the Macleay system forbids their having an independent set of affinities. On this subject, however, there IS as yet much ohscurity, and it nntst be left to future inquirers to clear it up. We must now call to mind that the geographical distri· bution of plants and animals was very different in the geological ages from \Vhat it is now. Down to a tilne not long antecedent to man, the same vegetation overspread every clime, and a similar uniformity marked the zoology. This is conceived by M. llrogniart, with great plausibility to have been the result of a uniformity of climate, produced by the as yet unexhausted effect of the internal heat of the earth upon its surface ; whereas climate has si nee depended chiefly on external sources of heat, as modified by the various meteorological influences. However the early uniform climate was produced, certain it is that, from about the close of the geological epoch, plants and animals have been dispersed over the globe with a regard to their particular characters, and specimens of both are found so 1solated in particular situation~, as utterly to exclude the idea that they came thither from any common centre. It may he asked-Considering that, in the geological epoch, species are not limited to particular regions, and that since the close of that epoch, they are very peculiarly limited, are we to presume the present organisms of the world to have been created ab initio after that time ? To this it m~y be answered-Not necessarily, as it so happens that _animals begin to be much varied, or to appear in a consid~ rable. variety of species, towards the close of the geolo glcal h1story. It may have been that the tnnltitudes of locally peculiar species only came into being after tho • ANIMATED NATURE. 135 uniform eli r:nate ~ad passed away. It may L4..ve only been ~hen a vaned cl.I!fiate arose; that fhe originally few speCies branc~ed off Into the present extensive variety. A ~.ues~LOn of a ver~ int~resting kind will now probably .anse In the r~ader s mind- f·Vhat place or status is ~.sszgn~d !o rru!-n 't'f! t~e new natural system? Before going 1?to thts tnquny, It IS necessary to advert to several parhcul~ rs of the natural system not yet noticed. I~ 1~ n~ce~sary, in p3:rticu~ar, to a~certain the grades which exist 1n the class1ficahon of animals. In the line o~ the .aves, Mr. Swainson finds these to be nine, the speCies p1ca, for example, being thus indicated:- Kingdom Sub-kingdom Class • • Order Tribe Family • Sub-family Genus . . . Sub-genus or species Animalia. Vertebrata. Aves. I ncessores. Conirostres Corvidre. Corvinre. Corvus. Pica. . This br~ngs us down to species, the subdivision where 1nter~arnage or breeding is usually considered as natural to an1~als, and where a resemblance of offspring to pa~ ents 1s generally persevered in. The dog, for instance, IS a spec1es, because all dogs can breed together, and the progeny .part~k~s of the appea~ances .of t~e parents. The human I ace Is. held as a species, pnmanly for the same reason. Species, however, is liable to another subdivision, whi.ch nat,ualists call variety; and variety appears to ~e subject to exactly the same.system of representation ~luch has bee? trac~d in species and higher denominations. In cants, for Instance, .the bull-dog and mastiff represent tl~e ferocwus suh- typical group; the water-dog 1s nataton~l; we se~ the speed and length of n1uzzle of ~b; snctonal group .In the greyhound.; and the bushy tail and gentle and serviCeable character of the rasorial in the sh~pel'd's dog and spaniel. Even the striped and spotted sk1n ?f the .t1ger and panther is reproduced in the more ferocw~s kmd of dogs-an indication of a fundamental connexwn between .Physical a11d mental qaualities which we have also seen In the zebra, and which is likewisP |