The Primary Factors of Organic EvolutionOpen Court Publishing Company, 1904 - 547 pages |
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acquired characters adult American Naturalist anagenesis anagenetic ancestors animals appears articulations Artiodactyla Batrachia become body bones canine Carboniferous Carnivora carpus cells Cetacea changes coiling color Condylarthra condyle Cope Creodonta crests cusps cyrtoceran degeneracy dentition digits Diplarthra direction disuse effect elbow-joint embryo energy Eocene evidence evolution existence external fact fishes forms function genera genus germ-plasma Glires groove growth gwyniform gyroceran humerus Hyatt impact impressed zone incisors increase inferior molars inherited kinetogenesis larvæ latter less limbs lower jaw Mammalia mastication ment metapodial modifications motion movements muscle muscular natural selection nautilian nautiloids normal observed ontogeny organic origin paleontology parallel Perissodactyla Phenacodus phylogeny plants posterior present primitive probably produced protoplasm pupa radius reproduction Reptilia result Ryder segments shell side similar skeleton soma species stage stimuli strain structure superior molars surface tion tissue tritubercular ulna Ungulata variations vertebral vertebral column Vertebrata whorl young
Popular passages
Page 4 - 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 180 - In each line of progression in the Terebratellidae, the acceleration of the period of reproduction, by the influence of environment, threw off genera which did not go through the complete series of metamorphoses, but are otherwise fully adult, and even may show reversional tendencies due to old age ; so that nearly every stage passed through by the higher genera has a fixed representative in a lower genus. Moreover, the lower genera are not merely equivalent to, or in exact parallelism with the early...
Page 4 - But if variations useful to any organic being ever do occur, assuredly individuals thus characterised will have the best chance of being preserved in the struggle for life; and from the strong principle of inheritance, these will tend to produce offspring similarly characterised. This principle of preservation, or the survival of the fittest, I have called Natural Selection.
Page 249 - I mean by this expression that the whole organisation is so tied together during its growth and development, that when slight variations in any one part occur, and are accumulated through natural selection, other parts become modified.
Page 462 - For peculiar habits confined to the workers or sterile females, however long they might be followed, could not possibly affect the males and fertile females, which alone leave descendants. I am surprised that no one has hitherto advanced this demonstrative case of neuter insects, against the well-known doctrine of inherited habit, as advanced by Lamarck.
Page 4 - ... to their geometrical rate of increase, a severe struggle for life at some age, season, or year, and this certainly cannot be disputed ; then, considering the infinite complexity of the relations of all organic beings to each other and to their conditions of life, causing an infinite diversity in structure, constitution, and habits, to be advantageous to them, it would be a most extraordinary fact if no variations had ever occurred useful to each being's own welfare, in the same manner as so many...
Page 4 - Nevertheless, low and simple forms will long endure if well fitted for their simple conditions of life. Natural selection, on the principle of qualities being inherited at corresponding ages, can modify the egg, seed, or young, as easily as the adult. Amongst many animals, sexual selection will have given its aid to ordinary selection, by assuring to the most vigorous and best adapted males the greatest...
Page 462 - ... into each other, but are perfectly well defined ; being as distinct from each other as are any two species of the same genus, or rather as any two genera of the same family. Thus in Eciton, there are working and soldier neuters, with jaws and instincts extraordinarily different : in Cryptocerus, the workers of one caste alone carry a wonderful sort of shield on their heads...
Page 11 - Through a great series of generations the germinal protoplasm retains its specific properties, dividing in every reproduction into an ontogenetic portion, out of which the individual is built up, and a phylogenetic portion which is reserved to form the reproductive material of the mature offspring. This reservation of the phylogenetic material I described as the continuity of the germ protoplasm.
Page 180 - B 0* ~ i i 3 o i 3 an adolescent condition. Similar comparisons may be made in the other genera. Progressively through each series, the adult structure of any genus forms the last immature stage of the next higher, until the highest member in its ontogeny represents serially, in its stages of growth, all the adult structures, with the larval and immature stages of the simpler genera.