Comentarios de la gente - Escribir un comentario
Otras ediciones - Ver todas
adapted admit affinities allied species America analogous ancient appear beak become bees believe belonging birds breeds cause cells characters cirripedes climate closely allied colour continuous crossed crustaceans degree developed difficulty distinct species doubt effects eggs embryo existing extinct extremely facts favourable females fertilised fertility flowers formations formerly forms fossil 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 kind larvae less living male mammals manner Marsupials migration modified descendants natural selection naturalists nearly nest occasionally occur oceanic islands offspring organisation organs parent peculiar perfect pigeon pistil pollen present principle probably produced quadrupeds ranked reciprocal crosses remarked reproductive resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive supposed swimbladder theory tion variability variations varieties vary whilst whole wings young
Página 1 - These facts, as will be seen in the latter chapters of this volume, seemed to throw some light on the origin of species — that mystery of mysteries, as it has been called by one of our greatest philosophers.
Página 1 - ... of our greatest philosophers. On my return home, it occurred to me, in 1837, that something might perhaps be made out on this question by patiently accumulating and reflecting on all sorts of facts which could possibly have any bearing on it. After five years' work I allowed myself to speculate on the subject, and drew up some short notes...
Página 424 - Analogy would lead me one step further, namely, to the belief that all animals and plants have descended from some one prototype. But analogy may be a deceitful guide.
Página 50 - In these several senses, which pass into each other, I use for convenience' sake the general term of Struggle for Existence.
Página 322 - Every species has come into existence coincident both in space and time with a pre-existing closely allied species.
Página 146 - 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 310 - I strongly insisted, in 1839 and 1845, on this " law of the succession of types,"—on " this wonderful relationship in the same continent between the dead and the living." Professor Owen has subsequently extended the same generalisation to the mammals of the Old World. We see the same law in this author's restorations of the extinct and gigantic birds of New Zealand. We see it also in the birds of the caves of Brazil. Mr. Woodward has shown that the same law holds good with sea-shells, but, from...
Página 57 - Now the number of. mice is largely dependent, as every one knows, on the number of cats; and Col.
Página 103 - It is a truly wonderful fact—the wonder of which we are apt to overlook from familiarity—that all animals and all plants throughout all time and space should be related to each other in groups subordinate to groups, in the manner which we everywhere behold...