On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeEaston Press, 1976 - 470 páginas |
Dentro del libro
Resultados 1-3 de 22
Página 258
... produce sterile hybrids . On the other hand , one species in a group will sometimes resist great changes of conditions with unimpaired fertility ; and certain species in a group will produce unusually fertile hybrids . No one can tell ...
... produce sterile hybrids . On the other hand , one species in a group will sometimes resist great changes of conditions with unimpaired fertility ; and certain species in a group will produce unusually fertile hybrids . No one can tell ...
Página 262
... hybrids when crossed inter se . If , on the other hand , a hybrid is crossed with either pure parent - species , the ... produced within the limits of the same species by the improper union of certain forms , whilst ordinary hybrids are ...
... hybrids when crossed inter se . If , on the other hand , a hybrid is crossed with either pure parent - species , the ... produced within the limits of the same species by the improper union of certain forms , whilst ordinary hybrids are ...
Página 268
... hybrids in the first generation , in contrast with that in the succeeding ... produced from nearly related species , follow according to Gärtner the same ... produced from a reciprocal cross , generally resemble each other closely ; and ...
... hybrids in the first generation , in contrast with that in the succeeding ... produced from nearly related species , follow according to Gärtner the same ... produced from a reciprocal cross , generally resemble each other closely ; and ...
Contenido
VARIATION UNDER NATURE | 30 |
STRUGGLE FOR EXISTENCE | 45 |
NATURAL SELECTION | 59 |
Derechos de autor | |
Otras 13 secciones no mostradas
Otras ediciones - Ver todas
Términos y frases comunes
accumulated adapted admit affinities allied species America ancient appear beak become bees believe belonging birds breeds cause cells characters climate closely allied colour common progenitor continuous crossed crustaceans degree developed difficulty distinct species divergence doubt effects eggs embryo existing exterminated extinct extremely facts favourable fertilised fertility flowers formation forms fossil Fritz Müller genera genus geological geological period gradations greater number groups of species habits Hence hybrids hybrids produced important increase individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living male mammals manner marsupials migration modified descendants natural selection naturalists nearly nest occasionally offspring organisation organs Origin of Species parent peculiar perfect pigeons pistil plants pollen present preserved principle probably produced quadrupeds ranked reciprocal crosses remarked resemblance rudimentary seeds slight South America stamens sterility structure struggle successive supposed swimbladder theory variability variations varieties vary whilst whole wings young