The Origin of Species by Means of Natural Selection: Or, The Preservation of Favored Races in the Struggle for Life, Volumen1D. Appleton & Company, 1889 |
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Página 51
... genera - Many of the species of the larger genera resemble varieties in being very closely , but un- equally , related to each other , and in having restricted ranges . BEFORE applying the principles arrived at in the last chapter to ...
... genera - Many of the species of the larger genera resemble varieties in being very closely , but un- equally , related to each other , and in having restricted ranges . BEFORE applying the principles arrived at in the last chapter to ...
Página 54
... genera of insects and of Brachiopod shells . In most polymorphic genera some of the species have fixed and definite characters . Genera which are polymorphic in one country seem to be , with a few exceptions , polymorphic in other ...
... genera of insects and of Brachiopod shells . In most polymorphic genera some of the species have fixed and definite characters . Genera which are polymorphic in one country seem to be , with a few exceptions , polymorphic in other ...
Página 55
... genera , variations which are of no service or disservice to the species , and which consequently have not been seized on and rendered definite by natural selection , as hereafter to be explained . Individuals of the same species often ...
... genera , variations which are of no service or disservice to the species , and which consequently have not been seized on and rendered definite by natural selection , as hereafter to be explained . Individuals of the same species often ...
Página 58
... genera . Under genera , including the most polymorphic forms , Mr. Babington gives 251 species , whereas Mr. Bentham gives only 112 , -a difference of 139 doubtful forms ! Amongst animals which unite for each birth , and which are ...
... genera . Under genera , including the most polymorphic forms , Mr. Babington gives 251 species , whereas Mr. Bentham gives only 112 , -a difference of 139 doubtful forms ! Amongst animals which unite for each birth , and which are ...
Página 68
... Genera in each Country vary more frequently than the Species of the Smaller Genera . If the plants inhabiting a country , as described in any Flora , be divided into two equal masses , all those in the larger genera ( i.e. , those ...
... Genera in each Country vary more frequently than the Species of the Smaller Genera . If the plants inhabiting a country , as described in any Flora , be divided into two equal masses , all those in the larger genera ( i.e. , those ...
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Términos y frases comunes
adapted advantage allied analogous animals and plants appear Asa Gray beak become bees believe birds breeds caudicle cause cells characters climate closely Cloth colour common crossed cuckoo degree descendants developed difficulty distinct species disuse domestic animals domestic races doubt effects eggs existence extinct extremely facts favourable females flowers forms Fritz Müller genera genus gradations greater number groups habits Hence hermaphrodites hive-bee important improved inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ large number larger genera larvæ less likewise males manner Mivart modified natural selection naturalists nearly nest neuters occasionally offspring organisation organs origin ORIGIN OF SPECIES parent perfect period pigeons pollen pollen-grains present preserved principle probably produced progenitor quadrupeds rank Red Grouse remarked resemble rock-pigeon seeds sexes sexual sexual selection slight stamens structure struggle sub-breeds supposed swimbladder tend tendency tion transitional tree tumbler pigeon variability variations varieties vary widely wild wings young
Pasajes populares
Página 227 - If it could be proved that any part of the structure of any one species had been formed for the exclusive good of another species, it would annihilate my theory, for such could not have been produced through natural selection.
Página 203 - If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.
Página 75 - Several writers have misapprehended or objected to the term Natural Selection, Some have even imagined that natural selection induces variability, whereas it' implies only the. preservation of such variations as arise and are beneficial to the being under its conditions of * life.
Página xxv - As many more individuals of each species are born than can possibly survive ; and as, consequently, there is a frequently recurring straggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected.
Página xix - In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history.
Página 144 - It is well known that several animals, belonging to the most different classes, which inhabit the caves of Carniola and of Kentucky, are blind. In some of the crabs the foot-stalk for the eye remains, though the eye is gone; — the stand for the telescope is there, though the telescope with its glasses has been lost. As it is difficult to imagine that eyes, though useless, could be in any way injurious to animals living in darkness, their loss may be attributed to disuse.
Página 55 - Nothing is easier than to admit in words the truth of the universal struggle for life, or more difficult — at least I have found it so — than constantly to bear this conclusion in mind.
Página 341 - Cloth, $2.00. DIFFERENT FORMS OF FLOWERS ON PLANTS OF THE SAME SPECIES. With Illustrations. 12mo. Cloth, $1.50. THE POWER OF MOVEMENT IN PLANTS. By CHARLES DARWIN, LL. D., FRS, assisted by FRANCIS DARWIN.
Página 140 - The limbs divided into great branches, and these into lesser and lesser branches, were themselves once, when the tree was small, budding twigs; and this connection of the former and present buds by ramifying branches may well represent the classification of all extinct and living species in groups subordinate to groups.
Página 140 - The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth. The green and budding twigs may represent existing species ; and those produced during each former year may represent the long succession of extinct species.