the existence
in the same community of in the same community of 1872 |
of 1859 1860 1861 1866 1869 |
two or three defined castes of workers or sterile
female female 1869 1872 | females 1859 1860 1861 1866 |
ants; ants; 1872 |
in the same community of ants; 1859 1860 1861 1866 |
ants in the same community; 1869 |
but I have attempted to show how
these these 1861 1866 1869 1872 | this 1859 1860 |
difficulties difficulties 1861 1866 1869 1872 | difficulty 1859 1860 |
can be mastered. |
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With respect to the almost universal sterility of species when first crossed, which forms so remarkable a contrast with the almost universal fertility of varieties when crossed, I must refer the reader to the recapitulation of the facts given at the end of the
ninth ninth 1872 | eighth 1859 1860 1861 1866 1869 |
chapter, which seem to me conclusively to show that this sterility is no more a special endowment than is the incapacity of two
distinct kinds of trees distinct kinds of trees 1872 |
trees 1859 1860 1861 |
distinct trees 1866 1869 |
to be grafted
together; together; 1860 1861 1866 1869 1872 | together, 1859 |
but that it is incidental on
....... 1866 1869 1872 | constitutional 1859 1860 1861 |
differences
confined to confined to 1866 1869 1872 | in 1859 1860 1861 |
the reproductive systems of the intercrossed species. We see the truth of this conclusion in the vast difference in the
results results 1869 1872 | result, 1859 1860 1861 1866 |
of crossing of crossing 1869 1872 | when 1859 1860 1861 1866 |
the same two species
reciprocally,— reciprocally,— 1869 1872 |
are crossed reciprocally; 1859 1860 1861 |
are crossed reciprocally,— 1866 |
that is, when one species is first used as the father and then as the
mother. mother. 1859 1860 1861 1872 | mother: 1866 1869 |
Analogy Analogy 1872 | analogy 1866 1869 |
from the consideration of dimorphic and trimorphic plants clearly leads
to
the same conclusion, for when the forms are illegitimately united, they yield few or no seed, and their offspring are more or less sterile; and these forms
belong to belong to 1872 | of 1866 1869 |
the same undoubted
species, species, 1872 | species 1866 1869 |
and
differ
from each other in no respect from each other in no respect 1872 |
in no respect from each other 1866 1869 |
except in their reproductive organs and functions. |
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Although the Although the 1861 1866 1869 1872 | The 1859 1860 |
fertility of varieties when intercrossed and of their mongrel offspring
has been asserted by so many authors to be universal, this cannot has been asserted by so many authors to be universal, this cannot 1861 1866 1869 1872 |
cannot 1859 1860 |
be considered
as quite correct after the facts given on the high authority of Gärtner and Kölreuter. as quite correct after the facts given on the high authority of Gärtner and Kölreuter. 1872 |
as universal; nor is their very general fertility surprising when we remember that it is not likely that either their constitutions or their reproductive systems should have been profoundly modified. 1859 1860 |
correct after the facts given on the authority of Gärtner and Kölreuter. 1861 1866 1869 |
↑1 blocks not present in 1859 1860 1861 1872; present in 1866 1869 | Nor is the very general fertility of varieties, when crossed, surprising, when we remember that it is not likely that their reproductive systems should have been profoundly modified.
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Most of the varieties which Most of the varieties which 1872 |
Moreover, most of the varieties which 1859 1860 1866 1869 |
Nor is the very general fertility of varieties, when crossed, surprising, when we remember that it is not likely that either their constitutions or their reproductive systems should 1861 |
have been
experimented on experimented on 1866 1869 1872 |
experimentised on 1859 1860 |
profoundly modified. Moreover, most of the varieties which 1861 |
have been
produced produced 1859 1860 1866 1869 1872 |
experimented on have been produced 1861 |
under domestication; and as domestication
(I do not mean mere confinement) almost certainly (I do not mean mere confinement) almost certainly 1866 1869 1872 |
apparently 1859 |
(I do not mean mere confinement) apparently 1860 1861 |
tends to eliminate
that sterility which, judging from analogy, would have affected the parent-species if intercrossed, that sterility which, judging from analogy, would have affected the parent-species if intercrossed, 1872 |
sterility, 1859 1860 1861 1866 1869 |
we ought not to expect
that domestication would likewise induce sterility in their modified descendants when crossed. that domestication would likewise induce sterility in their modified descendants when crossed. 1872 |
it also to produce sterility. 1859 1860 1861 1866 1869 |
This elimination of sterility apparently follows from the same cause which allows our domestic animals to breed freely under diversified circumstances; and this again apparently follows from their having been gradually accustomed to frequent changes in their conditions of life. |
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A double and parallel series of facts seems to throw much light on the sterility of species, when first crossed, and of their hybrid offspring. On the one side, there is good reason to believe that slight changes in the conditions of life give vigour and fertility to all organic beings. We know also that a cross between the distinct individuals of the same variety, and between distinct varieties, increases the number of their offspring, and certainly gives to them
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