Comentarios de usuarios - Escribir una reseña
No hemos encontrado ninguna reseña en los sitios habituales.
Otras ediciones - Ver todo
according action adapted admit advantage allied America amount animals appear become believe belonging birds breeds called cause certain characters climate closely colour common considered continuous crossed descendants developed difficulty distinct domestic doubt effects existing extinct extremely facts families favourable fertility flowers follow formations forms genera genus give given greater groups habits hand Hence hybrids important increase individuals inhabitants inherited insects instance instincts intermediate islands kind known laws less living look male manner means modified namely natural selection naturalists nearly never observed occur offspring organs origin parent perfect period plants points present preserved principle probably produced ranked reason remarked resemblance respect seeds seems seen separated shown side similar single slight sometimes species stage sterility structure successive supposed tend theory variability variations varieties various vary whole widely young
Página 64 - It may be said that natural selection is daily and hourly scrutinising, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life.
Página 63 - 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 61 - If such do occur, can we doubt (remembering that many more individuals are born than can possibly survive) that individuals having any advantage, however slight, over others, would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed.
Página 160 - 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 48 - It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms ; for in this case there can be no artificial increase of food, and no prudential restraint from marriage.
Página 380 - What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include similar bones, in the same relative positions?
Página 144 - 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 61 - 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 xvii - 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.