The Evolution of SexHumboldt, 1889 - 322 pages |
Contents
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Common terms and phrases
active amoeboid anabolic anabolism and katabolism asexual asexual reproduction become Beneden birds body Brooks buds carpels cell-substance chromatin chromatin elements ciliated colonies colour conjugation continuous contrast crustaceans Darwin degenerate differentiation dimorphic division ducts egg-cell eggs embryo emphasised essential evolution extrusion fact favour female cells female organs fertilisation fishes flowers frog functions gemmules germ-plasma germinal vesicle growth Hensen heredity hermaphroditism Hertwig higher animals hydroid illustrations important individual infusorians insects larvæ less male and female male cell male elements mammals maturity Maupas multiplication natural selection naturalists normal nuclear elements nucleus nutritive observed occur offspring origin ovary ovum parasitic parent parthenogenesis passive physiological plants polar globules predominant preponderance primitive produce protoplasm Protozoa recognised regard reproductive cells reproductive elements reproductive organs result Rolph rotifers secondary sexual characters sex-cells sexual reproduction sexual selection species sperm spermatozoa sponges stage structure theory threadworm tion unisexual usually variations Weismann yolk
Popular passages
Page 275 - Gavest thou the goodly wings unto the peacocks? Or wings and feathers unto the ostrich? Which leaveth her eggs in the earth, And warmeth them in the dust, And forgetteth that the foot may crush them, Or that the wild beast may break them. She is hardened against her young ones, As though they were not hers...
Page 38 - I formerly thought that when a tendency to produce the two sexes in equal numbers was advantageous to the species, it would follow from natural selection, but I now see that the whole problem is so intricate that it is safer to leave its solution for the future.
Page 9 - To sum up on the means through which, as far as we can judge, sexual selection has led to the development of secondary sexual characters. It has been shown that the largest number of vigorous offspring will be reared from the pairing of the strongest and best-armed males...