The American Naturalist, Volume 52Essex Institute, 1918 - Biology |
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Aleppo aleurone algæ allelomorphs Andalusian animals appear Apterous awns bacteria Barred Plymouth Rocks birds blue blue-splashed breeding cells cent characters chromosome color Colorless coral cotyledons cross cross-over ratio curve Cynips Drosophila evidence evolution exchange ratios F₂ fact factor mutations fantail females fish flock forked forms gall gambeli gametes gene genera genetic green hatched Hawaiian heredity heterozygous homozygous hybrids individuals inheritance Lake Clear larvæ length male mated maturity Mendelian mice moult mutations normal number of eggs oats occur offspring organism pair parent parthenogenetic Pearl phase phase rule pigment Pima plants Plymouth Rocks present probably progenies pubescence pullets races records reefs relation Rhode Island Reds rhythm rubidus Schlechtendalia seed-coat sexual sexual reproduction shown sonoriensis species Table tail feathers temperature theory tion tissues variability variation whitefish winter egg production yellow zygote
Popular passages
Page 480 - It seems likely, however, that the idea of "interacting limiting factors" explains his facts better than that of the optimum. The idea of limiting factors in experimental work is now building up a laboratory idea of environmental complexity, even under controlled conditions, which corresponds closely with what the field ecologists have called an environmental complex. This is a healthy sign as it will greatly assist in the correlation of field and laboratory studies. Recently Livingston ('17, p....
Page 479 - When several factors are possibly controlling a function, a small increase or decrease of the factor that is limiting, and of that factor only, will bring about an alternation of the magnitude of the functional activity. Probably this formulation should be broader, and be made to include not only a single factor, but all unfavorable or limiting factors, as I have indicated above, and as both Livingston ('17, p. 8) and as Hooker ('17, p. 201) suggest.
Page 127 - Nat. Acad. Sci., 2, p. 240. Davenport, CB 1916. The Form of Evolutionary Theory that Modern Genetical Research Seems to Favor. AM. NAT., 50, pp. 449-465. Glaser, OC 1916. The Basis of Individuality in Organisms. Sci., NS, 44, pp. 219-224. Goodspeed, TH, and Clausen, RE 1917a.
Page 470 - Surely in meteorology, as in astronomy, the thing to hunt down is a cycle, and if that is not to be found in the temperate zone, then go to the frigid zones, or the torrid zones and look for it, and if found, then above all things, and in whatever manner, lay hold of, study it, record it, and see what it means.
Page 479 - When the magnitude of a function is limited by one of a set of possible factors, increase of that factor, and of that one, alone, will be found to bring about an increase of the magnitude of the function . . . (p.
Page 273 - EM EAST BUSSEY INSTITUTION", HARVARD UNIVERSITY THE establishment of methods of reproduction which maintain variation and inheritance mechanisms on a high plane of efficiency is naturally a fundamental requirement in organic evolution. Since, however, inheritance mechanisms presumably equivalent are common to every method, of reproduction, one should be able to interpret the evolutionary tendencies in the matter by comparing their effectiveness in offering selective agencies their raw material. Some...
Page 117 - ... lamarckiana are but the emergence into a state of homozygosis, through crossing over, of recessive factors constantly present in the heterozygous stock. Proof of the spuriousness of some of the mutations in Oenothera is, however, not an argument against the validity of the modern mutation theory; the fact of real mutation has been amply demonstrated in Drosophila as well as elsewhere, and it should be emphasized that these mutations can here be distinguished...
Page 477 - ... nature were different. The biologist finds in it no self-sustaining power and no reality that would endure if it were abstracted from the natural world of which it is a part. Surely, this is good sense and good science. No physiologist who studies the waste and repair of living bodies, no naturalist who knows living beings in their homes, no embryologist who studies the influence of external conditions upon development, can for an instant admit that living beings are selfsufficient or self-sustaining,...
Page 416 - ... have considered in the preceding pages the peculiarities of form and structure characterizing the reef formations bordering islands and continents, and their influence upon the enclosed land. Could we raise one of these coral-bound islands from the waves, we should find that the reefs stand upon the submarine slopes, like massy structures of artificial masonry ; some forming a broad flat platform or shelf ranging around the land, and others encircling it like vast ramparts, perhaps a hundred...
Page 284 - ... there be any difference at all between the two forms, he is left with only one reasonable hypothesis to account for everything, Mendelian segregation and recombination. Mendelian heredity is a manifestation of sexual reproduction. Wherever it occurs, there Mendelian heredity will be found. Now if N variations occur in the germplasm of an asexually reproducing organism, only N types can be formed to offer raw material to selective agencies. But if N variations occur in the germ plasm of a sexually...