On the Origin of Species by Means of Natural Selection; Or, The Preservation of Favoured Races in the Struggle for LifeD. Appleton, 1861 - 440페이지 |
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18 페이지
... larva will almost certainly entail changes in the mature animal . In monstrosities , the correlations between quite distinct parts are very curious ; and many instances are given in Isidore Geoffroy St. Hilaire's great work on this ...
... larva will almost certainly entail changes in the mature animal . In monstrosities , the correlations between quite distinct parts are very curious ; and many instances are given in Isidore Geoffroy St. Hilaire's great work on this ...
82 페이지
... larvæ . So , conversely , modifications in the adult will probably often affect the structure of the larva ; but in all cases natural selection will ensure that modifications consequent on other modifications at a dif- ferent period of ...
... larvæ . So , conversely , modifications in the adult will probably often affect the structure of the larva ; but in all cases natural selection will ensure that modifications consequent on other modifications at a dif- ferent period of ...
116 페이지
... larva . Von Baer's standard seems the most widely applicable and the best ; namely , the amount of differentiation of the differ- ent parts ( in the adult state , as I should be inclined to add ) , and their specialisation for different ...
... larva . Von Baer's standard seems the most widely applicable and the best ; namely , the amount of differentiation of the differ- ent parts ( in the adult state , as I should be inclined to add ) , and their specialisation for different ...
130 페이지
... larva , will , it may safely be concluded , affect the structure of the adult ; in the same manner as any malconformation affecting the early embryo , seriously affects the whole organisation of the adult . The several parts of the body ...
... larva , will , it may safely be concluded , affect the structure of the adult ; in the same manner as any malconformation affecting the early embryo , seriously affects the whole organisation of the adult . The several parts of the body ...
170 페이지
... larva of the dragon - fly and in the fish Cobites . In the Hydra , the animal may be turned inside out , and the ex- terior surface will then digest and the stomach respire . In such cases natural selection might easily specialise , if ...
... larva of the dragon - fly and in the fish Cobites . In the Hydra , the animal may be turned inside out , and the ex- terior surface will then digest and the stomach respire . In such cases natural selection might easily specialise , if ...
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accumulated adapted affinities allied species America amount ancient animals appear become bees believe birds breeds cause cells characters cirripedes climate closely allied colour continuous crossed crustaceans degree difficulty distinct species disuse divergence domestic doubt embryo endemic Europe existing exterminated extinct extremely facts favourable fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hermaphrodites hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing intermediate larvæ laws less living look male mammals manner migration modification modified descendants natural selection naturalists nearly nest offspring organic organisation perfect pigeons pistil plants pollen present probably produced progenitor ranked reciprocal crosses remarked resemble rudimentary seeds seems sexual selection Silurian slight South America sterility structure struggle successive suppose swimbladder tend theory tion trees variability variation varieties vary whole widely
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9 페이지 - After five years' work I allowed myself to speculate on the subject, and drew up some short notes; these I enlarged in 1844 into a sketch of the conclusions, which then seemed to me probable: from that period to the present day I have steadily pursued the same object. I hope that I may be excused for entering on these personal details, as I give them to show that I have not been hasty in coming to a decision.
76 페이지 - When we reflect on this struggle, we may console ourselves with the full belief, that the war of nature is not incessant, that no fear is felt, that death is generally prompt, and that the vigorous, the healthy, and the happy survive and multiply.
171 페이지 - 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.
9 페이지 - Beagle,' as naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America, and in the geological relations of the present to the past inhabitants of that continent.
70 페이지 - Firs on the distant hill-tops ; within the last ten years large spaces have been enclosed, and self-sown firs are now springing up in multitudes, so close together that all cannot live. When I ascertained that these young trees had not been sown or planted, I was so much surprised at their numbers that I went to several points of view, whence I could examine hundreds of acres of the unenclosed heath, and literally I could not see a single Scotch Fir, except the old planted clumps.
72 페이지 - Near villages and small towns I have found the nests of humble-bees more numerous than elsewhere, which I attribute to the number of cats that destroy the mice." Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice and then of bees, the frequency of certain flowers in that district!
72 페이지 - Newman, who has long attended to the habits of humble-bees, believes that " more than two-thirds of them are thus destroyed all over England.
169 페이지 - To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.
423 페이지 - Hereafter we shall be compelled to acknowledge that the only distinction between species and well-marked varieties is, that the latter are known, or believed to be connected at the present day by intermediate gradations whereas species were formerly thus connected.
212 페이지 - This difficulty, though appearing insuperable, is lessened, or, as I believe, disappears, when it is remembered that selection may be applied to the family, as well as to the individual, and may thus gain the desired end. Thus, a well-flavoured vegetable is cooked, and the individual is destroyed; but the horticulturist sows seeds of the same stock, and confidently expects to get nearly the same variety; breeders of cattle wish the flesh and fat to be well marbled together; the animal has been slaughtered,...