Origin of Species Variorum

→ OMIT 1869 1872

excepting in the first main divisions; 1859 1860 1861 1866

→ and embryo, are 1869 1872

are 1859 1860 1861 1866

→ of structure in such parts not 1869

not 1872

↑ 4 blocks not present in 1869 1872; present in 1859 1860 1861 1866

We must not, therefore, in classifying, trust to resemblances in parts of the organisation, however important they may be for the welfare of the being in relation to the outer world. 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.

↑ 7 blocks not present in 1869; present in 1859 1860 1861 1866 1872

That the mere physiological importance of an organ does not determine its 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 Proteaceæ, 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 Connaraceæ "differ in having one or more ovaria, in the existence or absence of albumen, in the imbricate or valvular æstivation. 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 antennæ, 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 antennæ in these two divisions of the same order are of unequal physiological importance. Any number of instances could be given of the varying importance for classification of the same important organ within the same group of beings.

the more important it becomes for classification. As an instance: Owen, in speaking of the dugong, says, "The generative

organs

organs,

being those which are most remotely related to the habits and food of an animal, I have always regarded as affording very clear indications of its true affinities. We are least likely in the modifications of these organs to mistake a merely adaptive for an essential character."

....

with

With

plants

plants,

how remarkable it is that the organs of vegetation, on which their

whole

nutrition and

life

depends,

depend,

are of little

signification,

signification;

→OMIT whereas the organs of reproduction, with their product the

seed,

seed

→and embryo, are of paramount importance! So again in formerly discussing

certain

....

morphological

characters

differences

which are not

functionally

physiologically

important, we have seen that they are often of the highest service in classification. This depends on their constancy throughout many allied groups; and

their

the

constancy

chiefly depends

depends chiefly

on any slight deviations →of structure in such parts not having been preserved and accumulated by natural selection, which acts only on

serviceable

useful

characters. ↑ ↑

That the mere physiological importance of an organ does not determine its classificatory value, is almost proved by the 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 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 Proteaceæ, 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 Connaraceæ