The Variation of Animals and Plants Under Domestication, 2권D. Appleton, 1898 - 495페이지 |
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analogous animals and plants Antirrhinum appear become birds bred breeders breeds buds capsules cattle cause cells changed conditions chapter characters climate close interbreeding colour common correlation crossed degree diseases distinct species dogs domestic races domesticated animals doubt effects extremely facts feathers female fertilised fertility flowers fowls Fritz Müller fruit Gard Gardener's Chronicle Gärtner gemmules given hair Hist horns horses hybrids increased individuals inherited insects instance Isidore Geoffroy Saint-Hilaire kind Kölreuter large number larvæ liable maize male manner modified natural selection natural species nectarine niata Notylia observed occasionally offspring Oncidium flexuosum organs ovules pangenesis Paraguay parent parent-forms Parthenogenesis peculiar peloric period petals pigeons pigs pistil pollen pollen-grains prepotent probably produced progenitor propagated racter remarks reproductive respect result reversion seed seedlings seen sheep slight stamens sterility stripes structure tendency tion transmitted variability variations varieties various vary whilst wild yield Youatt Zoological Gardens
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427 페이지 - ... no shadow of reason can be assigned for the belief that variations, alike in nature and the result of the same general laws, which have been the ground-work through natural selection of the formation of the most perfectly adapted animals in the world, man included, were intentionally and specially guided. However much we may wish it, we can hardly follow Professor Asa Gray in his belief 'that variation has been led along certain beneficial lines, like a stream, along definite and useful lines...
370 페이지 - These granules may be called gemmules. They are collected from all parts of the system to constitute the sexual elements, and their development in the next generation forms a new being ; but they are likewise capable of transmission in a dormant state to future generations and may then be developed.
350 페이지 - I venture to advance the hypothesis of Pangenesis, which implies that everj' separate part of the whole organisation reproduces itself. So that ovules, spermatozoa, and pollen-grains, — the fertilised egg or seed, as well as buds, — include and consist of a multitude of germs thrown off from each separate part or...
54 페이지 - ... the seeds of the many varieties of our culinary and agricultural plants; in the caterpillar and cocoon stages of the varieties of the silkworm; in the eggs of poultry, and in the colour of the down of their chickens; in the horns...
349 페이지 - I am aware that my view is merely a provisional hypothesis or speculation ; but, until a better one be advanced, it will serve to bring together a multitude of facts which are at present left disconnected by any efficient cause.
426 페이지 - I may recur to the metaphor given in a former chapter; if an architect were to rear a noble and commodious edifice, without the use of cut stone, by selecting from the fragments at the base of a precipice wedge-formed stones for his arches, elongated stones for his lintels, and flat stones for his roof, we should admire his skill and regard him as the paramount power. Now, the fragments of stone, though indispensable to the architect, bear to the edifice built by him the same relation which the fluctuating...
397 페이지 - In a highly-organised animal, the gemmules thrown off from each different unit throughout the body must be inconceivably numerous and minute. Each unit of each part, as it changes during development, and we know that some insects undergo at least twenty metamorphoses, must throw off its gemmules. But the same cells may long continue to increase by self-division, and even become modified by absorbing peculiar nutriment, without necessarily throwing off modified gemmules.
250 페이지 - Vilmorin, 18 even maintains that, when any particular variation is desired, the first step is to get the plant to vary in any manner whatever, and to go on selecting the most variable individuals, even though they vary in the wrong direction; for the fixed character of the species being once broken, the desired variation will sooner or later appear.
401 페이지 - ... changes to which the world has been subject; but domesticated productions will often have been exposed to more sudden changes and to less continuously uniform conditions. As man has domesticated so many animals and plants belonging to widely different classes, and as he certainly did not choose with prophetic instinct those species which would vary most, we may infer that all natural species, if exposed to analogous conditions, would, on an average, vary to the same degree.
21 페이지 - From these facts we may perhaps infer that the degraded state of so many half-castes is in part due to reversion to a primitive and savage condition, induced by the act of crossing, as to well as the unfavourable moral conditions under which they generally exist.