The Origin of SpeciesP.F. Collier, 1909 - 552 páginas |
Otras ediciones - Ver todas
Términos y frases comunes
adapted admit affinities allied species America ancient appear Asa Gray beak become bees believe belonging birds breeds cause cells characters climate closely allied colour common continent crossed crustaceans degree developed difficulty distinct species domestic doubt eggs embryo existing extinct extremely facts favourable fertilised fertility flowers formation forms fossil Fritz Müller genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hybrids important increase individuals inhabitants inherited insects instance instincts intercrossing intermediate lamellæ larvæ less living male mammals manner Marsupials migration modified descendants natural selection naturalists nearly nest oceanic islands offspring organisation organs parent peculiar perfect pigeons pistil pollen present principle probably produced progenitor quadrupeds ranked reciprocal crosses remarked resemblance rudimentary seeds sexual selection slight South America stamens sterility structure successive supposed tend theory tion variability variations varieties vary whilst whole wings young
Pasajes populares
Página 97 - Nature's productions should be far " truer " in character than man's productions ; that they should be infinitely better adapted to the most complex conditions of life, and should plainly bear the stamp of far higher workmanship...
Página 210 - 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 398 - Every species has come into existence coincident both in space and time with a pre-existing closely allied species.
Página 78 - 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 192 - 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 23 - ... and as, consequently, there is a frequently recurring struggle 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. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.
Página 22 - ... species had not been independently created, but had descended, like varieties, from other species. Nevertheless, such a conclusion, even if well founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and coadaptation which justly excites our admiration.
Página 94 - 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 46 - We cannot suppose that all the c — ac x1 breeds were suddenly produced as perfect and as useful as we now see them ; indeed, in many cases, we know that this has not been their history. The key is man's power of accumulative selection : nature gives successive variations ; man adds them up in certain directions useful to him.
Página 88 - Throw up a handful of feathers, and all must fall to the ground according to definite laws ; but how simple is this problem compared to the action and reaction of the innumerable plants and animals which have determined, in the course of centuries, the proportional numbers and kinds of trees now growing on the old Indian ruins...