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Export to Excel select * from OriginOfSpecies where subject = '13 - Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Or' order by subject, title, ordinal limit 4, 4 (Page 2: Row)
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13 - Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Or 13-03 - Rules and difficulties in classification, explained on the theory of descent with modification 30 Perhaps from this cause it has partly arisen, that almost all naturalists lay the greatest stress on resemblances in organs of high vital or physiological importance.

No doubt this view of the classificatory importance of organs which are important is generally, but by no means always, true.

But their importance for classification, I believe, depends on their greater constancy throughout large groups of species; and this constancy depends on such organs having generally been subjected to less change in the adaptation of the species to their conditions of life.

That the mere physiological importance of an organ does not determine the classificatory value, is almost shown by the one fact, that in allied groups, in which the same organ, as we have every reason to suppose, has nearly the same physiological value, its classificatory value is widely different.

No naturalist can have worked at any group without being struck with this fact; and it has been most fully acknowledged in the writings of almost every author.

It will suffice to quote the highest authority, Robert Brown, who in speaking of certain organs in the Proteaceae, says their generic importance, `like that of all their parts, not only in this but, as I apprehend, in every natural family, is very unequal, and in some cases seems to be entirely lost.' Again in another work he says, the genera of the Connaraceae `differ in having one or more ovaria, in the existence or absence of albumen, in the imbricate or valvular aestivation.

Robert Brown
Robert Brown

Proteaceae
Proteaceae
13 - Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Or 13-03 - Rules and difficulties in classification, explained on the theory of descent with modification 40 Any one of these characters singly is frequently of more than generic importance, though here even when all taken together they appear insufficient to separate Cnestis from Connarus.' To give an example amongst insects, in one great division of the Hymenoptera, the antennae, as Westwood has remarked, are most constant in structure; in another division they differ much, and the differences are of quite subordinate value in classification; yet no one probably will say that the antennae in these two divisions of the same order are of unequal physiological importance.

cnestis
cnestis

connarus
connarus

hymenoptera
hymenoptera


Any number of instances could be given of the varying importance for classification of the same important organ within the same group of beings.

Again, no one will say that rudimentary or atrophied organs are of high physiological or vital importance; yet, undoubtedly, organs in this condition are often of high value in classification.

No one will dispute that the rudimentary teeth in the upper jaws of young ruminants, and certain rudimentary bones of the leg, are highly serviceable in exhibiting the close affinity between Ruminants and Pachyderms.

Robert Brown has strongly insisted on the fact that the rudimentary florets are of the highest importance in the classification of the Grasses.
13 - Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Or 13-03 - Rules and difficulties in classification, explained on the theory of descent with modification 50 Numerous instances could be given of characters derived from parts which must be considered of very trifling physiological importance, but which are universally admitted as highly serviceable in the definition of whole groups.

For instance, whether or not there is an open passage from the nostrils to the mouth, the only character, according to Owen, which absolutely distinguishes fishes and reptiles the inflection of the angle of the jaws in Marsupials -- the manner in which the wings of insects are folded mere colour in certain Algae mere pubescence on parts of the flower in grasses the nature of the dermal covering, as hair or feathers, in the Vertebrata.

fish
fish

reptile
reptile

marsupials
marsupials


If the Ornithorhynchus had been covered with feathers instead of hair, this external and trifling character would, I think, have been considered by naturalists as important an aid in determining the degree of affinity of this strange creature to birds and reptiles, as an approach in structure in any one internal and important organ.

ornithorhynchus
ornithorhynchus
13 - Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Or 13-03 - Rules and difficulties in classification, explained on the theory of descent with modification 60 The importance, for classification, of trifling characters, mainly depends on their being correlated with several other characters of more or less importance.

The value indeed of 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 characters, 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 classification 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 Linnaeus, that the characters do not give the genus, but the genus gives the characters; for this saying seems founded on an appreciation of many trifling points of resemblance, too slight to be defined.

Certain plants, belonging to the Malpighiaceae, bear perfect and degraded flowers; in the latter, as A. de Jussieu has remarked, `the greater number of the characters proper to 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 years, 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 sagaciously saw, as Jussieu observes, that this genus should still be retained amongst the Malpighiaceae.


Antoine Laurent de Jussieu
Antoine Laurent de Jussieu