Darwin was clearly talking about natural selection leading to a form adapted to the conditions that the creature found itself in. The creature continues to perfect its functions and form to meet the local conditions. The underlined portion of your first quote supports that interpretation.
The last part of the second paragraph you quote expresses his wonder at the beauty of the amazing variety. No surprise, we are capable of wonder. The first part says that in Darwin's view natural selection leads to complexity, and he tags the more complex animals as "higher animals". He could just as easily said "more complex animals".
My earlier comment was making the point that Darwin did not see "improvement" from a strictly anthropocentric view- his concept of "better" was a form more adapted to its local conditions. Many read Darwin from a human viewpoint, that "more evolved" means more perfect from our point of view and not from the viewpoint of the process. Thus, the concept that we humans are "more evolved" than some other species and therefore "better" than that other.
So a complex creature gradually changing to a less complex one to meet the demands of its environment is, to Darwin, improvement and advancement. To many people I have spoken with, this Darwinian betterment is seen as degradation, downward evolution, or devolution.
He did not see evolution as necessarily leading to a crown of creation, an endpoint of perfection, some evolutionary goal, but change to adapt.
http://www.gutenberg.org/etext/2009
Actually evolution is not change in order to adapt. It is simply change.
If there are variants that have statistically more offspring than other variants, then their alleles will become more common in the population.
If the available variants don't include better adaptations, extinction is always a possibility. But the variants don't know where they are headed.
Sorry. You parse words and ask us what "is" is. I cited your source himself.
Read him without your "change for change's sake" goggles on.
Furthermore, I have a long, distant history of dealing with such issues on this board, and have shown repeatedly by the writings of the evols themselves, how so much of evolution's arguments amount to nothing more than silly, circular, semantic games.
Do a search and you'll see that your position - along with those of your cohort here - has already been more than adequately addressed and refuted.
Buh-bye.