Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then 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.
In looking for the gradations by which an organ in any species has been perfected, we ought to look exclusively to its lineal ancestors; but this is scarcely ever possible, and we are forced in each case to look to species of the same group, that is to the collateral descendants from the same original parent-form, in order to see what gradations are possible, and for the chance of some gradations having been transmitted from the earlier stages of descent, in an unaltered or little altered condition.
In the Articulata we can commence a series with an optic nerve merely coated with pigment, and without any other mechanism; and from this low stage, numerous gradations of structure, branching off in two fundamentally different lines, can be shown to exist, until we reach a moderately high stage of perfection.
Look at the family of squirrels; here we have the finest gradation from animals with their tails only slightly flattened, and from others, as Sir J.
Seeing this gradation
and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.
The geometric distribution of the air voids throughout the concrete specimen would be unknown; however, in the development of the method presented herein, it was assumed that all of the air voids were spherical in shape and displayed gradations with varying skewness.
Given that the chord length index does not provide an accurate estimate of the air void content, an accurate estimate of the air void gradation curve in concrete specimens is needed.
Flex Clear Drive technology achieves high density, smooth color gradation
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On the cardboard's surface Dole-Recio has painted circles, sometimes rounds within squares, in various shaded gradations
and then covered them with various cloudy stripes-frost, periwinkle, slate-leaving only the ghostliest residue of the circles.
The new DiMAGE Scan Elite II provides users with rich tonal gradation
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6 Dmax, this scanner delivers crisp scans with rich, true colors, better shadow detail, and smoother gradations
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s highest rating, "recommended status," the CD6100 provides brilliant, accurate colors, smooth gradations
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2 -- including Agfa's unique 4-bit ABS patented screening algorithms -- optimizes print quality in solid color areas, tints, blends and gradations
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They said Patwaris were working in Khyber Pakthunkhwa in grade-V, awaiting promotion and up gradation
over several years.