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according acid American amount analyses animals appears aurora become bismuth body called carbon cause character closely coal color common compared considerable considered containing continued crystals described determined direction effect elements equal evidence existing experiments extended fact feet flora force fossil genera genus given gives heat important inches increase individuals interesting Journal known Lake least length less light mass matter means metal meteor miles mineral mountains natural nearly noticed object observations obtained occur organic origin pass period plants portion position present probably produced Prof question referred regard relations remains remarkable river rocks seen Sept side similar species specimens substance supposed surface theory tion variation varieties volume weight whole
Página 176 - I cannot doubt that the theory of descent with modification embraces all the members of the same great class or kingdom. I believe that animals are descended from at most only four or five progenitors, and plants from an equal or lesser number.
Página 148 - As all the living forms of life are the lineal descendants of those which lived long before the Cambrian epoch, we may feel certain that the ordinary succession by generation has never once been broken, and that no cataclysm has desolated the whole world. Hence we may look with some confidence to a secure future of great length. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection.
Página 147 - Judging from the past, we may safely infer that not one living species will transmit its unaltered likeness to a distant futurity. And of the species now living very few will transmit progeny of any kind to a far distant futurity...
Página 158 - The limbs divided into great branches, and these into lesser and lesser branches, were themselves once, when the tree was...
Página 170 - There is no exception to the rule that every organic being naturally increases at so high a rate that, if not destroyed, the earth would soon be covered by the progeny of a single pair.
Página 170 - 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 174 - But if variations useful to any organic being ever do occur, assuredly individuals thus characterised will have the best chance of being preserved in the struggle for life ; and from the strong principle of inheritance, these will tend to produce offspring similarly characterised. This principle of preservation, or the survival of the fittest, I have called Natural Selection.
Página 159 - ... in a fossil state. As we here and there see a thin straggling branch springing from a fork low down in a tree...
Página 449 - THE BOYDEN PREMIUM URIAH A. BOYDEN, ESQ., of Boston, Mass., has deposited with THE FRANKLIN INSTITUTE the sum of one thousand dollars, to be awarded as a premium to "Any resident of North America who shall determine by experiment whether all rays of light,* and other physical rays, are or are not transmitted with the same velocity.
Página 158 - The green and budding twigs may represent existing species ; and those produced during former years may represent the long succession of extinct species. At each period of growth all the growing twigs have tried to branch out on all sides, and to overtop and kill the surrounding twigs and branches, in the same manner as species and groups of species have at all times overmastered other species in the great battle for life.