| → it was instinct 1869 1872 |
| instinct 1861 1866 |
|
| → varied. 1869 1872 |
| slightly changed; nor can we conjecture by what gradations many instincts have been developed when they relate to organs (such as the mammary glands) on the first origin of which we know nothing. 1861 1866 |
|
| → were independently acquired through 1869 1872 |
| have been acquired by independent acts of 1859 1860 1861 |
| have been independently acquired by 1866 |
|
|
Some birds build their nests of mud, believed to be moistened with saliva; and one of the swifts of North America makes its nest (as I have seen) of sticks agglutinated with saliva, and even with flakes of this substance. Is it then very improbable that the natural selection of individual swifts, which secreted more and more saliva, should at last produce a species with instincts leading it to neglect other materials, and to make its nest exclusively of inspissated saliva? And so in other cases. It
admitted that in many instances we cannot conjecture whether
→it was instinct
or structure
first
→varied.
|
|
| No doubt many instincts of very difficult explanation could be opposed to the theory of natural
cases, in which we cannot see how an instinct could
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
→were independently acquired through
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
|
