The American Naturalist, Volume 43Essex Institute, 1909 |
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adaptation adult algæ America animals appear behavior bird breeding cent cestodes characters chromosomes color corn crayfishes crinoids crossed cuticula Darwin dk.br eggs elementary species evidence evolution experiments fact factor female fertilization fishes flowers forms genera genus germ cells give grams gray growth gynandromorph hair heredity heterozygote hybrids important individuals inheritance insects kelps lamina large number larva larvæ later Lessoniopsis lt.br male Mendelian Mendelian inheritance ment mice muscular articulations mutation natural selection observations offspring old stallions organs origin Origin of Species ovary ovum oyster pairs pangen paper parenchyma parent pigment pinnule plants ponds present probably problem produced Professor race region relation seeds seems sired spawning specimens spermatophores spermatozoa sporophytic stages stipe structure subcuticular subcuticular cells syzygies tadpoles temperature theory tion toads trematodes variability variations varieties Vries weight worms yellow
Popular passages
Page 164 - This has been effected chiefly through the natural selection of numerous successive, slight, favourable 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.
Page 79 - One of the most remarkable features in our domesticated races is that we see in them adaptation, not indeed to the animal's or plant's own good, but to man's use or fancy.
Page 160 - If numerous species, belonging to the same genera or families, have really started into life at once, the fact would be fatal to the theory of evolution through natural selection.
Page 69 - No man would ever try to make a fantail till he saw a pigeon with a tail developed in some slight degree in an unusual manner, or a pouter...
Page 139 - We are thus brought to the question which has been largely discussed by naturalists, namely, whether species have been created at one or more points of the earth's surface. Undoubtedly there are very many cases of extreme difficulty, in understanding how the same species could possibly have migrated from some one point to the several distant and isolated points, where now found. Nevertheless the simplicity of the view that each species was first produced within a single region captivates the...
Page 377 - ... 1 Papers from the Biological Laboratory of the Maine Agricultural Experiment Station. No.
Page 164 - ... and it has been stated that 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.
Page 165 - Several writers have misapprehended or objected to the term Natural Selection. Some have even imagined that natural selection induces variability, whereas it implies only the preservation of such variations as arise and are beneficial to the being under its conditions of life.
Page 145 - The direct action of changed conditions leads to definite or indefinite results. In the latter case the organisation seems to become plastic, and we have much fluctuating variability. In the former case the nature of the organism is such that it yields readily, when subjected to certain conditions, and all, or nearly all the individuals become modified in the same way.
Page 142 - ... to natural selection, by affording a better chance of the occurrence of profitable variations. Unless such occur, natural selection can do nothing. Under the term of " variations," it must never be forgotten that mere individual differences are included.