物种起源（英文全本）TXT下载-(英)达尔文 as、is-全文下载

I should

never have

anticipated

that

natural

selection

could have

been

efficient

in so high

a degree,

had not

the case

of these

neuter

insects

convinced

me of the

fact. I

have,

therefore,

discussed

this case,

at some

little but

wholly

insufficient

length, in

order to

show the

power of

natural

selection,

and

likewise

because

this is by

far the

most

serious

special

difficulty,

which my

theory has

encountered.

The case,

also, is

very

interesting,

as it