Comparison with 1859 |
|
birth, but which wander little and
which which 1859 1860 1861 1866 | which 1869 1872 |
can increase at a
very very 1859 1860 1861 1866 1869 | very 1872 |
rapid rate, a new and improved variety might be quickly formed on any one spot, and might there maintain itself in a
body, body, 1859 1860 1861 1866 | body 1869 1872 |
so that whatever intercrossing took place would be chiefly between so that whatever intercrossing took place would be chiefly between 1859 1860 1861 1866 |
and afterwards spread, so that the crossing would be chiefly between 1869 |
and afterwards spread, so that 1872 |
the individuals of the
same new variety. same new variety. 1859 1860 1861 1866 |
new variety living together in the same place. 1869 |
new variety would chiefly cross together. 1872 |
A local variety when once thus formed might subsequently slowly spread to other districts. On
the above the above 1859 1860 1861 1866 | this 1869 1872 |
principle, nurserymen always prefer
getting getting 1859 1860 1861 1866 | saving 1869 1872 |
seed from a large body of
plants plants 1859 1860 1861 1866 | plants, 1869 1872 |
of of 1859 1860 1861 1866 | as 1869 1872 |
the
same variety, as the same variety, as the 1859 1860 1861 1866 |
OMIT 1869 1872 |
chance of intercrossing
with other varieties with other varieties 1859 1860 1861 1866 |
OMIT 1869 1872 |
is thus lessened. |
|
Even
in the case of slow-breeding in the case of slow-breeding 1859 1860 1861 1866 |
in the case of 1869 |
with 1872 |
animals, animals, 1859 1860 1861 1866 | animals 1869 1872 |
which unite
for each birth,
we we 1859 1860 1861 1866 1869 |
and which do not propagate rapidly, we 1872 |
must not
overrate overrate 1859 1860 1861 1866 |
assume that 1869 |
assume that free intercrossing would always eliminate 1872 |
the effects of
intercrosses in retarding intercrosses in retarding 1859 1860 1861 1866 |
OMIT 1869 1872 |
natural selection;
for
I can bring
a considerable catalogue a considerable catalogue 1859 1860 1861 1866 |
a considerable body 1869 |
forward a considerable body 1872 |
of
facts, facts, 1859 1860 1861 1866 1869 | facts 1872 |
showing that within the same area,
varieties varieties 1859 1860 1861 1866 1869 | two varieties 1872 |
of the same animal
can can 1859 1860 1861 1866 | may 1869 1872 |
long remain distinct, from haunting different stations, from breeding at slightly different seasons, or from
varieties of the same kind varieties of the same kind 1859 1860 1861 1866 1869 |
the individuals of each variety 1872 |
preferring to pair together. |
|
Intercrossing plays a very important part in nature
in in 1859 1860 1861 1866 1869 | by 1872 |
keeping the individuals of the same species, or of the same variety, true and uniform in character. It will obviously thus act far more efficiently with those animals which unite for each birth;
but but 1859 1860 1861 1866 1869 | but, 1872 |
I have already attempted to show that I have already attempted to show that 1859 1860 1861 1866 |
as already stated 1869 |
as already stated, 1872 |
we have reason to believe that occasional intercrosses take place with all animals and
with all with all 1859 1860 1861 1866 1869 | with all 1872 |
plants. Even if these take place only at long
intervals, intervals, 1859 1860 1861 1866 | intervals 1869 1872 |
I am convinced that I am convinced that 1859 1860 |
of time, 1869 1872 |
OMIT 1861 1866 |
the young thus produced will gain so much in vigour and fertility over the offspring from long-continued self-fertilisation, that they will have a better chance of surviving and propagating their kind; and thus, in the long run, the influence of
intercrosses, intercrosses, 1859 1860 1861 1866 1869 | crosses, 1872 |
even at rare intervals, will be great.
If there exist If there exist 1859 1860 1861 1866 1869 |
With respect to 1872 |
organic beings
which never which never 1859 1860 1861 1866 1869 |
extremely low in the scale, which do not propagate sexually, nor conjugate, and which cannot possibly 1872 |
intercross, uniformity of character can be retained
amongst amongst 1859 1860 1861 1866 1869 | by 1872 |
them, them, 1859 1860 1861 1866 1869 | them 1872 |
as long as their as long as their 1859 1860 1861 1866 1869 |
under the same 1872 |
conditions of
life life 1859 1860 1861 1866 1869 | life, 1872 |
remain the same, remain the same, 1859 1860 1861 1866 1869 |
OMIT 1872 |
only through the principle of inheritance,
and through natural selection
destroying any which depart destroying any which depart 1859 1860 1861 1866 1869 |
which will destroy any individuals departing 1872 |
from the proper
type; type; 1859 1860 1861 1866 1869 | type. 1872 |
but if their but if their 1859 1860 1861 1866 1869 |
If the 1872 |
conditions of life change and
they they 1859 1860 1861 1866 1869 | the 1872 |
undergo undergo 1859 1860 1861 1866 1869 | form undergoes 1872 |
modification, uniformity of character can be given to
their their 1859 1860 1861 1866 1869 | the 1872 |
modified offspring, solely by natural selection preserving
the same the same 1859 1860 1861 1866 | similar 1869 1872 |
favourable variations. |
|
Isolation, also, is an important element in the
process of process of 1859 1860 1861 1866 |
changes effected through 1869 |
modification of 1872 |
natural natural 1859 1860 1861 1866 1869 |
species through natural 1872 |
selection. In a confined or isolated area, if not very large, the organic and inorganic conditions of life will generally be
in a great degree in a great degree 1859 1860 1861 1866 |
almost 1869 1872 |
uniform; so that natural selection will tend to modify all the
individuals of a varying species throughout the area individuals of a varying species throughout the area 1859 1860 1861 1866 |
varying individuals of the same species 1869 1872 |
in the same
manner manner 1859 1860 1861 1866 | manner. 1869 1872 |
in in 1859 1860 1861 1866 | in 1869 1872 |
relation relation 1859 1860 1861 1866 | relation 1869 1872 |
to to 1859 1860 1861 1866 | to 1869 1872 |
the the 1859 1860 1861 1866 | the 1869 1872 |
same same 1859 1860 1861 1866 | same 1869 1872 |
conditions. conditions. 1859 1860 1861 1866 | conditions. 1869 1872 |
Intercrosses, Intercrosses, 1859 1860 1861 1866 | Intercrossing 1869 1872 |
also, also, 1859 1860 1861 1866 | also, 1869 1872 |
with the
individuals individuals 1859 1860 1861 1866 | inhabitants 1869 1872 |
of the
same species, which otherwise would have inhabited the surrounding and differently circumstanced same species, which otherwise would have inhabited the surrounding and differently circumstanced 1859 1860 1861 |
same species, which othewise would have inhabited the surrounding and differently circumstanced 1866 |
surrounding 1869 1872 |
districts, districts, 1859 1860 1861 1866 | districts 1869 1872 |
will will 1859 1860 1861 1866 | will, 1869 1872 |
be be 1859 1860 1861 1866 |
also, be 1869 |
also, be thus 1872 |
prevented. |
Text in this page (from paragraph 3200, sentence 310 to paragraph 3200, sentence 310, word 25) is not present in 1859 |