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abdomen appear birds breeding castrated cells chro classes of sperm color Columbia University combinations condition conjugation cross Darwin diagram egg nucleus eggs eggs produce embryo evidence evolution evolution of sex fact factor for horns female Fig female-producing sperm fertilized eggs flies forms four gametes germ-cells give gray gray-red gynandromorph half heredity hermaphroditic hornless hybrid hydatina inbred individuals insects kinds long-winged males and females mating Mendel's Mendelian micronuclei mosomes normal male number of chromosomes offspring ovary paramcecium parent parthenogenetic parthenogenetic female polar bodies pollen race red-eyed male reproduction Rhabditis Sacculina secondary sexual characters self-fertilization sex chromo sex chromosomes sex factor sex glands sex ratio sex-determination sex-linked sex-linked characters sex-linked inheritance sexual egg sexual females sexual reproduction sexual selection shown species sperm spermatocyte spermatogenesis spermatozoa stage strains studied synapsis takes place theory tion vigor white eyes white-eyed male wings yellow
Page 103 - This depends, not on a struggle for existence, but on a struggle between the males for possession of the females ; the result is not death to the unsuccessful competitor, but few or no offspring. Sexual selection is, therefore, less rigorous than natural selection. Generally, the most vigorous males, those which are best fitted for their places in nature, will leave most progeny.
Page 286 - BLUMENTHAL LECTURES POLITICAL PROBLEMS OF AMERICAN DEVELOPMENT. By ALBERT SHAW, LL.D., Editor of the Review of Reviews.
Page 116 - ... admire or even notice this display. The hen, the turkey, and the pea-fowl go on feeding while the male is displaying his finery ; and there is reason to believe that it is his persistency and energy rather than his beauty which wins the day.
Page 103 - The result is not death to the unsuccessful competitor, but few or no offspring. Sexual selection is, therefore, less rigorous than . natural selection. Generally, the most vigorous males, those which are best fitted for their places in nature, will leave most progeny. But in many cases, victory depends not so much on general vigour, as on having special weapons, confined to the male sex.
Page 104 - I have seen the female sitting quietly on a branch, and two males displaying their charms in front of her. One would shoot up like a rocket, then suddenly expanding the snow-white tail like an inverted parachute, slowly descend in front of her, turning around gradually to show off both back and front.
Page 105 - The expanded white tail covered more space than all the rest of the bird, and was evidently the grand feature in the performance.
Page 285 - York The Press was incorporated June 8, 1893, to promote the publication of the results of original research. It is a private corporation, related directly to Columbia University by the provisions that its Trustees shall be officers of the University and that the President of Columbia University shall be President of the Press. The publications of the Columbia University Press include works on Biography, History, Economics, Education, Philosophy, Linguistics, and Literature, and the following series:...
Page 286 - Price, $1.50 net. THE PRINCIPLES OF POLITICS FROM THE VIEWPOINT OF THE AMERICAN CITIZEN. By JEREMIAH W. JENKS, LL.D., Professor of Political Economy and Politics in Cornell University. 12mo, cloth, pp. xviii + 187. Price, $1.50 net.
Page 117 - In this chapter he described many of the dances, songs, and love-antics of birds, but regarded all such phenomena as merely "periodical fits of gladness." While, however, we may quite well agree with Mr. Hudson that conscious sexual gratification on the part of the female is not the cause of music and dancing performances in birds, nor of the brighter colors and ornaments that distinguish the male, such an opinion by no means excludes the conclusion that these phenomena are primarily sexual and intimately...