The Law of Heredity: A Study of the Cause of Variation, and the Origin of Living OrganismsJ. Murphy, 1883 - 336페이지 |
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xi 페이지
... crossing - Two kinds of reversion- Summary ... CHAPTER VII . THE EVIDENCE FROM VARIATION . Causes of variation - Changed conditions of life induce varia- bility - No particular kind of change is necessary - Varia- bility is almost ...
... crossing - Two kinds of reversion- Summary ... CHAPTER VII . THE EVIDENCE FROM VARIATION . Causes of variation - Changed conditions of life induce varia- bility - No particular kind of change is necessary - Varia- bility is almost ...
18 페이지
... crossing is not the same when crosses are made reciprocally . 11. The sex of the parent - species affects the degree of variability of hybrids ; and when a hybrid is used as the father , and either one of the pure parent - species , or ...
... crossing is not the same when crosses are made reciprocally . 11. The sex of the parent - species affects the degree of variability of hybrids ; and when a hybrid is used as the father , and either one of the pure parent - species , or ...
61 페이지
... crossed with a drone of the Ital- ian bee she produces hybrid workers , while her male offspring are all pure German bees . In certain Lepidoptera , as in the bees , parthenogene- sis seems to be normal , and it has been observed in ...
... crossed with a drone of the Ital- ian bee she produces hybrid workers , while her male offspring are all pure German bees . In certain Lepidoptera , as in the bees , parthenogene- sis seems to be normal , and it has been observed in ...
74 페이지
... crossed with the female of another species or variety , the hybrid offspring is often very different from that which is produced when the female of the first species is crossed with the male of the second . If the function of the ovum ...
... crossed with the female of another species or variety , the hybrid offspring is often very different from that which is produced when the female of the first species is crossed with the male of the second . If the function of the ovum ...
86 페이지
... discord , and sterility from crossing be compared with the darkness re- sulting from the interference of waves of light . " Such symbolism will harmonize with the peculiar reproduction , before mentioned , of heads in the body 86 Heredity .
... discord , and sterility from crossing be compared with the darkness re- sulting from the interference of waves of light . " Such symbolism will harmonize with the peculiar reproduction , before mentioned , of heads in the body 86 Heredity .
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acquired action adult alike allied species ancestor ancestral form asexual asexual reproduction become birds body breed cause of variation changed conditions characteristics color common conclusion crossing crustacea Daphnia Darwin Darwin says descendants domesticated pigeons embryo epigenesis evolution existence explanation fact favor female fertilized fortuitous fowls functions furnishes gemmules genera genus germ germinative vesicle give rise gradually greater greatly hereditary homology horns hybrids hydroids hypothesis individual influence inherited insects latent law of heredity male cell male element medusa ment modification natural selection offspring ordinary origin of species ovum pangenesis parent parthenogenesis peculiarities perfect phenomena present produced race reasons for believing reciprocal crosses reproductive elements resemblance result secondary sexual characters sexes sexual elements sexual reproduction sexual selection similar simply striped structure tendency to vary theory of heredity throw off gemmules tion transmission transmit true variable various women young
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272 페이지 - Let this process go on for millions of years; and during each year on millions of individuals of many kinds; and may we not believe that a living optical instrument might thus be formed as superior to one of glass, as the works of the Creator are to those of man?
47 페이지 - Lastly, I assume that the gemmules in their dormant state have a mutual affinity for each other, leading to their aggregation into buds or into the sexual elements.
256 페이지 - The principal and most characteristic aberration of speculative minds as such, consists precisely in the deficiency of this lively perception and ever-present sense of objective fact. For want of this, they often not only overlook the contradiction which outward facts oppose to their theories, but lose sight of the legitimate purpose of speculation altogether, and let...
229 페이지 - Just as man can improve the breed of his gamecocks by the selection of those birds which are victorious in the cockpit, so it appears that the strongest and most vigorous males, or those provided with the best weapons, have prevailed under nature, and have led to the improvement of the natural breed or species.
272 페이지 - ... the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real.
274 페이지 - ... guidance of methodical selection. The comparison would be in every way fairer with the effects which follow from unconscious selection, that is the preservation of the most useful or beautiful animals, with no intention of modifying the breed ; but by this process of unconscious selection, various breeds have been sensibly changed in the course of two or three centuries.
260 페이지 - Their imaginations individualise more ; their affections are, in consequence, concentrated rather on leaders than on causes ; and if they care for a great cause, it is generally because it is represented by a great man, or connected with some one whom they love. In politics, their enthusiasm is more naturally loyalty than patriotism. In history, they are even more inclined than men to dwell exclusively upon biographical incidents or characteristics as distinguished from the march of general causes....
268 페이지 - ... be the case. The advantage, whatever it may be, is utterly outbalanced by numerical inferiority. A million creatures are born; ten thousand survive to produce offspring. One of the million has twice as good a chance as any other of surviving, but the chances are fifty to one against the gifted individuals being one of the hundred survivors. No doubt the chances are twice as great against any other individual, but this does not prevent their being enormously in favour of some average individual.
243 페이지 - ... members of the same group. The cause of this seems to lie in the males of almost all animals having stronger passions than the females.
136 페이지 - These several conditions alone render it probable that variability of every kind is directly or indirectly caused by changed conditions of life. Or, to put the case under another point of view, if it were possible to expose all the individuals of a species during many generations to absolutely uniform conditions of life, there would be no...