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Show 360 CLASSIFICATION. [CHAP. XIII. look at it merely as a scheme for arranging together those living objects which are most alike, and for separating those which are n1ost unlike; or as an artificial means for enunciating, as briefly as possible, general propositions,that is, by one sentence, to give the characters comn1on, for instance, to all mammals, by another those com1non to all carnivora, by another those common to the dog-genus and then by adding a single sentence, a full description i~ given of each kind of dog. The ingenuity and utility of this system are indisputable. But many naturalists think that something more is meant by the Natural System· they believe that it reveals the plan of the Creator · but unless it ~e specified whether order in , time or spa~e, or what else IS meant by the plan of the Creator, it seems to me tha~ nothing is thus added to ~ur knowledge. Such expressions as that famous one of Linnreus, and which we often meet with in a more or less concealed form, that the characters do not make the genus, but that the genus gives the characters, seem to imply that something more is included in our classification, than mere resemblance. I _beli~ve that soinething more is included ; and that propinquity of descent,-the only known cause of the similarity of organic beings,-is the bond, hidden as it is by various degrees of modification, which is partially revealed to us by our classifications. Let us now consider the rules followed in classification, and the difficulties which are encountered on the view that classification either gives some unknown plan of creation, or is simply a scheme for enunciating general propositions and of placing together the forms most like each other. It might have been thought (and was in ancient times thought) that those parts of the structure which de· termined the :habits of life, and the general place of each being in the economy of nature would be of very high importance in c.lassification. Nothing can be more false. No one regards the external sin1ilarity of a mouse to a shrew, of a dugong to a whale, of a whale to a fish, as of any importance. These resemblances, though so intimately connected with the whole life of the being, are ranked as merely "adaptive or analogical characters;" but to CHAP. XIII.] CLASSIFICATION. th 'd . 361 e cons1 e1·ation of thes recur. It may even be ei~:~emblances we shall have to less any part of the organg· t' as. a general rule that the h ab I·t s ,. the more I. mportanIsta iIto nb IS cone erne d W.i t' h special As an rnstance : Owen in s 1 ~COlnes for classification " Th e generati·v e organ's beinp ea nn(o)' of th. e d ugong, says,· motely related to the habits !nJ~ose whiCh are n1ost real ways regarded as affordi'ng oo1d of ~n animal, I have t rue af fi n1· ti·e s. We are least 1v.1e r1y c. e' ar In d1' cat·i ons of its these .organs to mistake a mer~fe Y J11 t~e modifications of character." So with plant J[ a aptive for an essential the organs of vegetation 0~ 0 'Y rema~kable it is that pends, are of little signific~tio which .thmr whole life dedivisions; whereas the or ann, e.xceptu~g in the first main product the seed, are of p~ra~ of r:Rroduction, with their We must not, therefore in ~In .I!ll;portance ! blances in parts of the organisa~~sify~g, trust :o resmnthey may be for the welfare of on,. o:vever Important outer world. Perhaps from thi;~e ben:~g In relation to the that almost all naturalists lay th a use It has partly arisen, blances in organs of hi h "t t greatest stress on rescm-tance. No doubt this vie~ o~\h o{ P.~ysiolog~cal imp orof organs which are important e .c assi catory lmportance ~eans always, true. But their i~ g~~erally, but by no twn, I believe, depends on th . mpoi tance for classifica-out large groups of species . e~n~e:~r constancy throughon such organs havin ' Is constancy depends cha~ge in the adaptatign ~f~heally b.een subj~cted to less of life. That the mere h . spe?IeS ~o thmr conditions organ does not determine Iftsy:li~~~liJ.ICal Importan?e of an shown by the one fact that in n· datory value, lS almost same organ as we h~v a Ie groups, in which the nearly the 'same h . el e':"ery reason to suppose has value is widely di/er!n~o offcal valu~, its classific~tory at any group without b~in o natural~st ca~ have worked has been most fully a k ~ struc~ With this fact . and it every author. It wil1 s~ffic edged In the wri~ings of almost ty, Robert Brown who in e to f~ote the hJghest authorithe Proteacere sa; h . spea. 111[5 of certain organs in of all their pa;ts n~t t O~lr e-e~h~lC blmportance, " like that 16 ' y In Is ut, as I apprehend, in |
