| → have been acquired by independent acts of 1859 1860 1861 |
| have been independently acquired by 1866 |
| were independently acquired through 1869 1872 |
|
| → being effected by 1859 1860 1861 1866 |
| having been effected through 1869 1872 |
|
|
have originated; cases, in which no intermediate gradations are known to exist; cases of instinct of
such trifling importance, that they could hardly have been acted on by natural selection; cases of instincts almost identically the same in animals so remote in the scale of nature, that we cannot account for their similarity by inheritance from a common
and
believe that they
→have been acquired by independent acts of
natural selection. I will not here enter on these several cases, but will confine myself to one special difficulty, which at first appeared to me insuperable, and actually fatal to
whole theory. I allude to the neuters or sterile females in insect-communities: for these neuters often differ widely in instinct and in structure from both the males and fertile females, and yet, from being sterile, they cannot propagate their kind. |
|
| The subject well deserves to be discussed at great length, but I will here take only a single case, that of working or sterile ants. How the workers have been rendered sterile is a difficulty; but not much greater than that of any other striking modification of structure; for it can be shown that some insects and other articulate animals in a state of nature occasionally become sterile; and if such insects had been social, and it had been profitable to the community that a number should have been annually born capable of work, but incapable of procreation, I can see no
difficulty in this
→being effected by
natural selection. But I must pass over this preliminary difficulty. The great difficulty lies in the working ants differing widely from both the males and the fertile females in structure, as in the shape of the
and in being destitute of wings and sometimes of eyes, and in instinct. As far as instinct alone is concerned, the
difference in this
|
