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Show 416 CLASSIFICATION. CHAP. XIII. in another division they differ much, an.d th~ differences are of quite subordinate value in classifica~Ion; yet no one pr.o b ab ly will say that the antennre In these two 1 h . 1 . divisions of the same order are of unequa p ysw O~lCal 1· mpor t anc e . Any number of instan. ces .c ould be given of the varying importance for classification o~ the same important organ within the same ~roup of bmngs. . Again, no one will say ~hat .rud1ment~ry ?r atrophied ans are of high phys1ologwal or vital 1m portance ; org . . a· . f f yet, undoubtedly, organs. 111 this con 1t1~n a~e o ten o high value in classific~tlon. No o~e w1ll dispute th~t the rudimentary teeth In the upper Jaws of young rununants and certain rudimentary bones of the leg, are highl~ serviceable in exhibiting the close affinity between Ruminants and Pachyderm.s. Robert Brown has strongly insisted on the fact th~t the rudi:nent~ry florets are of the highest importance In the classificatwn of the Grasses. Numerous instances could be given of characters derived from parts which must be cons~dered of : ery trifling physiological importanc~, but w~1Ich are un~v.ersally admitted as highly serviceable In the defimt10~1 of whole groups. For instance, whether or not there IS an open passage from the nostrils t? the mouth, t~e only character, according to Owen,. whiC~ absolutely d~stinguishes fishes and reptiles-the Inflectw~ of th~ angle of the jaws in Marsupials-the manner In ;vhwh t~e wings of insects are folded-mere colour In ce1-ta~n Algre-mere pubescence on parts of the flowe:· m . h . 01' grasses-the nature of the dermal covenng, . as au feathers in the Vertebrata. If the Ornithorhynchus had been co~ered with feathers instead of hair, this external and trifling character woul?, I think, hav~ b.een c~~~ sidered by naturalists as Important an aid In dot mining the degree of a ffi n1· ty of ' tlu ·s st I .a n ge crea' ture to CuAr. XIII. CLASSIFICATION. 417 ?irds an 1 d redp~iles, as an approach in structure in any one Interna an Important organ. The importance, for classification, of trifling character mainly depends on their being correlated with severai other characters of more or less importance. The value indeed o~ an aggregate of characters is very evident in natural history. Hence, as has often been remarked a species may depart from its allies in several charact~rs both of high physiological importance and of almost universal prevalence, and yet leave us in no doubt where it should be ranked. Hence, also, it has been found that a c~assification founded on any single character: however Important that may be, has always failed; for no part of the organisation is universally constant. The importance of an aggregate of characters, even when none. are important, alone explains, I think, that saying of L1nnmus, that the characters do not give the genus, but the genus gives the characters; for this sayinrr seems founded on an appreciation of many trifling point~ of rese~blance, too slight to be defined. Certain plants, belonging to the Malpighiaceoo, bear perfect and degraded flowers ; in the latter, as A. de J ussieu has remarked, :'the greater number of the characters proper t~ the species, to the genus, to the family, to the class, disappear, and thus laugh at our classification." But when Aspicarpa produced in France, during several !ears, only degraded flowers, departing so wonderfully In a number of the most important points of structure from . the proper type of the order, yet M. Richard sagacwusl.y saw, as J ussieu observes, that this genus ~ho.uld still be retained amongst the Malpighiaceoo. Th~s case seems to me well to illustrate the spirit with whwh our classifications are sometimes necessarily founded. Practically when naturalists are at work, they do T 3 |