物种起源（英文全本）-古代-(英)达尔文-小说txt下载-全集最新列表

reveals.

In the

first case

the two

sexual

elements

which go

to form

the embryo

are

perfect;

in the

second

case they

are either

not at all

developed,

or are

imper-

fectly

developed.

This

distinction

is

important,

when the

cause of

the

sterility,

which is

common to

the two

cases, has

to be

considered.

The

distinction

has

probably

been

slurred

over,

owing to

the

sterility

in both

cases

being

looked on

as a