A Winter's Tale by Shakespeare

[Abstract Idea]

Yet nature is made better by no mean
But nature makes that mean: so over that art
Which you say adds to nature, is an art
That nature makes.

I have read the quote by Shakespeare above in a physics book.
I keep rereading it once in a while. But I cannot understand it.
What is Shakespeare trying to express here? Is there any possible relation to physics?

[Soup]

See pages 2 and 3 here and pages 227 and 228 here.

[Kätzchen]

As far as I understand it, this passage is about changing plants through breeding. He explains that bred plants are still nature and not art, because human hand can improve nature, but the means to improve it is in itself nature.