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|OriginOfSpecies - 475 Rows|
|14 - Recapitulation and Conclusion||14-02 - Recapitulation of the general and special circumstances in its favour||30||
As geology plainly proclaims that each land has undergone great physical changes, we might have expected that organic beings would have varied under nature, in the same way as they generally have varied under the changed conditions of domestication.
And if there be any variability under nature, it would be an unaccountable fact if natural selection had not come into play.
It has often been asserted, but the assertion is quite incapable of proof, that the amount of variation under nature is a strictly limited quantity.
Man, though acting on external characters alone and often capriciously, can produce within a short period a great result by adding up mere individual differences in his domestic productions; and every one admits that there are at least individual differences in species under nature.
But, besides such differences, all naturalists have admitted the existence of varieties, which they think sufficiently distinct to be worthy of record in systematic works.
No one can draw any clear distinction between individual differences and slight varieties; or between more plainly marked varieties and subspecies, and species.
Let it be observed how naturalists differ in the rank which they assign to the many representative forms in Europe and North America.
|02 - Variations Under Nature||02-04 - Wide-ranging, much diffused, and common Species vary most||30||
With respect to the number of individuals or commonness of species, the comparison of course relates only to the members of the same group.
One of the higher plants may be said to be dominant if it be more numerous in individuals and more widely diffused than the other plants of the same country, which live under nearly the same conditions.
A plant of this kind is not the less dominant because some conferva inhabiting the water or some parasitic fungus is infinitely more numerous in individuals and more widely diffused.
But if the conferva or parasitic fungus exceeds its allies in the above respects, it will then be dominant within its own class.
|07 - Instinct||07-03 - Aphides and ants||30||
as in the case of corporeal structure, and conformably with my theory, the instinct of each species is good for itself, but has never, as far as we can judge, been produced for the exclusive good of others.
One of the strongest instances of an animal apparently performing an action for the sole good of another, with which I am acquainted, is that of aphides voluntarily yielding their sweet excretion to ants: that they do so voluntarily, the following facts show.
I removed all the ants from a group of about a dozen aphides on a dock-plant, and prevented their attendance during several hours.
After this interval, I felt sure that the aphides would want to excrete.
I watched them for some time through a lens, but not one excreted; I then tickled and stroked them with a hair in the same manner, as well as I could, as the ants do with their antennae; but not one excreted.
Afterwards I allowed an ant to visit them, and it immediately seemed, by its eager way of running about, to be well aware what a rich flock it had discovered; it then began to play with its antennae on the abdomen first of one aphis and then of another; and each aphis, as soon as it felt the antennae, immediately lifted up its abdomen and excreted a limpid drop of sweet juice, which was eagerly devoured by the ant.
Even the quite young aphides behaved in this manner, showing that the action was instinctive, and not the result of experience.
But as the excretion is extremely viscid, it is probably a convenience to the aphides to have it removed; and therefore probably the aphides do not instinctively excrete for the sole good of the ants.
Although I do not believe that any animal in the world performs an action for the exclusive good of another of a distinct species, yet each species tries to take advantage of the instincts of others, as each takes advantage of the weaker bodily structure of others.
So again, in some few cases, certain instincts cannot be considered as absolutely perfect; but as details on this and other such points are not indispensable, they may be here passed over.
|14 - Recapitulation and Conclusion||14-05 - Effects of its adoption on the study of Natural history||30||
A new variety raised by man will be a far more important and interesting subject for study than one more species added to the infinitude of already recorded species.
Our classifications will come to be, as far as they can be so made, genealogies; and will then truly give what may be called the plan of creation.
The rules for classifying will no doubt become simpler when we have a definite object in view.
We possess no pedigrees or armorial bearings; and we have to discover and trace the many diverging lines of descent in our natural genealogies, by characters of any kind which have long been inherited.
Rudimentary organs will speak infallibly with respect to the nature of long-lost structures.
Species and groups of species, which are called aberrant, and which may fancifully be called living fossils, will aid us in forming a picture of the ancient forms of life.