be born with an innate tendency to pursue certain kinds of prey. Nor can this be thought very improbable; for we often observe great differences in the natural tendencies of our domestic animals; one cat, for instance, taking to catch rats, another mice; one cat, according to Mr. St. John, bringing home winged game, another hares or rabbits, and another hunting on marshy ground and almost nightly catching woodcocks or snipes. The tendency to catch rats rather than mice is known to be inherited. Now, if any slight innate change of habit or of structure benefited an individual wolf, it would have the best chance of surviving and of leaving offspring. Some of its young would probably inherit the same habits or structure, and by the repetition of this process, a new variety might be formed which would either
supplant supplant 1859 1860 1861 | supplant, 1866 |
or coexist
with with 1859 1860 1861 | with, 1866 |
the
parent form of parent form of 1860 1861 1866 |
parent-form 1859 |
....... 1860 1861 1866 | of 1859 |
wolf. Or, again, the wolves inhabiting a mountainous district, and those frequenting the lowlands, would naturally be forced to hunt different prey; and from the continued preservation of the individuals best fitted for the two sites, two varieties
would would 1861 1866 | might 1859 1860 |
slowly be formed. These varieties would cross and blend where they met; but to this subject of intercrossing we shall soon have to return. I may add, that, according to Mr. Pierce, there are two varieties of the wolf inhabiting the Catskill Mountains in the United States, one with a light greyhound-like form, which pursues deer, and the other more bulky, with shorter legs, which more frequently attacks the
shepherd's shepherd's 1859 1860 1861 | shepher's 1866 |
flocks. |
Let us now take a Let us now take a 1859 1860 1861 1866 |
It may be worth while to give another and 1869 |
more complex
case. case. 1859 1860 1861 1866 |
illustration of the action of natural selection. 1869 |
↑1 blocks not present in 1859 1860 1861 1866 1869; present in 1872 | It may be worth while to give another and more complex illustration of the action of natural selection.
|
Certain plants excrete
a a 1859 1860 1861 1866 | a 1869 1872 |
sweet juice, apparently for the sake of
eliminating eliminating 1859 1860 1861 1869 1872 | elimi- nating 1866 |
something injurious
from from 1859 1860 1861 1866 1872 | from, 1869 |
their their 1859 1860 1861 1866 1869 | the 1872 |
sap: this is
effected effected 1859 1860 1861 1866 | effected, 1869 1872 |
by by 1859 1860 1861 1866 |
for instance, by 1869 1872 |
glands at the base of the stipules in some Leguminosæ, and at the
back back 1859 1860 1861 1866 | backs 1869 1872 |
of the
leaf leaf 1859 1860 1861 1866 | leaves 1869 1872 |
of the common laurel. This juice, though small in quantity, is greedily sought by
insects. insects. 1859 1860 1861 1866 |
insects; but their visits do not in any way benefit the plant. 1869 1872 |
Let us now suppose a little sweet Let us now suppose a little sweet 1859 1860 1861 1866 |
Now, let us suppose that the 1869 1872 |
|