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acters allelomorph animals and plants appear beans biogenetic law black vestigial body bred breed true bristles Castle char chromo color blind Darwin daugh Diagram illustrating Difflugia division dominant Drosophila Drosophila ampelophila embryos eosin evidence explanation eye color fact fertilized flies fruit fly genetic germ cells germ plasm gill slits give half heredity hooded rats hybrid inbred individuals Johannsen kinds lacticolor LONG GRAY LONG Mendel's law Mendelian mesothorax modifiers mutant factors Mutant race natural selection normal notch offspring organism pairs of characters paleontologist Paleontology Paramecium peas polar bodies produced race of fruit recessive red eyed female red eyed male result sex chromosomes sex linked characters sex linked inheritance shown in figure single sooty sperm stages tail takes place thorax tion variation vidual white eyed male wild fly wild species wild types wings X chromosome yellow
Page 72 - I am inclined to think that an overstatement to the effect that each factor may affect the entire body, is less likely to do harm than to state that each factor affects only a particular character.
Page 40 - It requires indeed some courage to undertake a labour of such far-reaching extent; this appears, however, to be the only right way by which we can finally reach the solution of a question the importance of which cannot be overestimated in connexion with the history of the evolution of organic forms. The paper now presented records the results of such a detailed experiment. This experiment was practically confined to a small plant group, and is now, after eight years...
Page 144 - With the discovery of this mechanism I venture the opinion that the problem of heredity has been solved. We know how the factors carried by the parent are sorted out to the germ cells. The explanation does not pretend to state how factors arise or how they influence the development of the embryo. But these have never been an integral part of the doctrine of heredity. The problems which they present must be worked out in their own field. So, I repeat, the mechanism of the chromosomes offers a satisfactory...
Page 15 - ... be disregarded. The Evidence from Embryology. In passing from the egg to the adult the individual goes through a series of changes. In the course of this development we see not only the beginnings of the organs that gradually enlarge and change into those of the adult animal, but also see some organs appear and later disappear before the adult stage is reached. We find, moreover, that the young sometimes resemble in a most striking way the adult stage of groups that we place lower in the scale...
Page 41 - The selection of the plant group which shall serve for experiments of this kind must be made with all possible care if it be desired to avoid from the outset every risk of questionable results. The experimental plants must necessarily — 1. Possess constant differentiating characters. 2. The hybrids of such plants must, during the flowering period, be protected from the influence of all foreign pollen or be easily capable of such protection.
Page 24 - ... between certain characters in the embryos of higher animals and corresponding stages in the embryos of lower animals is most plausibly explained by the assumption that they have descended from the same ancestors, and that their common structures are embryonic survivals. The Evidence from Paleontology. The direct evidence furnished by fossil remains is by all odds the strongest evidence that we have in favor of organic evolution.
Page 70 - Drosophila] called rudimentary wings has as its principle [principal] characteristic very short wings. But the factor for rudimentary wings also produces other effects as well. The females are almost completely sterile, while the males are fertile. The viability of the stock is poor. When flies with rudimentary wings are put into competition with wild flies relatively few of the rudimentary flies come through, especially if the culture is crowded. The hind legs are also shortened. All these effects...
Page 144 - I have passed in review a long series of researches as to the nature of the hereditary material. We have, in consequence of this work, arrived within sight of a result that a few years ago seemed far beyond our reach. The mechanism of heredity has, I think, been discovered — discovered not by a flash of intuition but as the result of patient and careful study of the evidence itself. "With the discovery of this mechanism I venture the opinion that the problem of heredity...
Page 67 - I may recall in this connection that wingless flies also arose in our cultures by a single mutation. We used to be told that wingless insects occurred on desert islands because those insects that had the best developed wings had been blown out to sea. Whether this is true or not, I will not pretend to say; but at any rate wingless insects may also arise, not through a slow process of elimination, but at a single step.
Page 194 - Evolution has taken place by the incorporation into the race of those mutations that are beneficial to the life and reproduction of the organism. Natural selection as here defined means both the increase in the number of individuals that results after a beneficial mutation has occurred (owing to the ability of living matter to propagate), and, also, that this preponderance of certain kinds of individuals in a population makes some further results more The Journal of Heredity probable than others....
From Google Scholar
Walter Garstang - 1922 - Journal of the Linnean Society of London, Zoology
Adolph H Schultz - 1924 - American Journal of Physical Anthropology
Th Dobzhansky - 1927 - Molecular Genetics and Genomics
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JEFFREY H SCHWARTZ
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