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adaptations altho animals animals and plants appear argument from ignorance biologists biology birds body carbon dioxide carbonic acid cell-division cell-theory cells centrosome changes characters chemical chlorophyll chromatin chromosomes classification color complex cytoplasm Darwin Darwinian definite distinction division dwarf earth eggs embryo energy environment essential evidence fact factors of evolution female fishes function fundamental germ germ-cells Hence heredity higher important individual inheritance inorganic insects kind known Lamarck lifeless matter living matter living substance living things males mammals membrane ment metabolism microscope mitosis modifications molecules natural selection naturalists nitrogen nucleus observed occur origin of species orthogenesis ovum oxygen physiology plants and animals present problems produced proteid protoplasm recognised reproduction resemblance result says Schleiden scientific seeds selection theory sexual sexual selection similar species-forming spontaneous starch structure theory of descent tion tissues to-day variation vertebrate vital phenomena
Página 225 - I attribute the modification of species exclusively to natural selection, I may be permitted to remark that in the first edition of this work, and subsequently, I placed in a most conspicuous position — namely, at the close of the Introduction — the following words : " I am convinced that natural selection has been the main but not the exclusive means of modification.
Página 132 - There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.
Página 180 - Here then I had at last got a theory by which to work ; but I was so anxious to avoid prejudice, that I determined not for some time to write even the briefest sketch of it.
Página 43 - I should expect to be a witness of the evolution of living protoplasm from not living matter. I should expect to see it appear under forms of great simplicity, endowed, like existing fungi, with the power of determining the formation of new protoplasm from such matters as ammonium carbonates, oxalates and tartrates, alkaline and earthy phosphates, and water, without the aid of light.
Página 187 - ... geometrical tendency to increase must be checked by destruction at some period of life. Our familiarity with the larger domestic animals tends, I think, to mislead us: we see no great destruction falling on them...
Página 200 - ... useful to any being. She can act on every internal organ, on every shade of constitutional difference, on the whole machinery of life. Man selects only for his...
Página 201 - Seeing that individual differences of the same kind perpetually recur, this can hardly be considered as an unwarrantable assumption. But whether it is true, we can judge only by seeing how far the hypothesis accords with and explains the general phenomena of nature. On the other hand, the ordinary belief that the amount of possible variation is a strictly limited quantity, is likewise a simple assumption. Although Natural Selection can act only through and...
Página 225 - ... variations; aided in an important manner by the inherited effects of the use and disuse of parts; and in an unimportant manner, that is, in relation to adaptive structures, whether past or present, by the direct action of external conditions, and by variations which seem to us in our ignorance to arise spontaneously. It appears that I formerly underrated the frequency and value of these latter forms of variation, as leading to permanent modifications of structure independently of natural selection.
Página 132 - It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth...
Página 201 - It may metaphorically be said that natural selection is daily and hourly scrutinizing, throughout the world, the slightest variations ; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wlicrcvcr opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life.