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acquired characters adaptive characters adduced animals appears argument argument from ignorance artificial selection become cause cessation of selection chapter climatic co-adaptation colour concerned congenital connexion continuity correlation Darwin Darwinian deduction definition degeneration degree distinction disuse doctrine due to natural epilepsy evidence experiments explain fact favour force of heredity Galton genera germ-plasm hereditary importance individuals inherited effects instincts kind Lamarck Lamarckian factors Lamarckian principles large proportional number less Lloyd Morgan matter merely modifications natural selection naturalists necessarily niata observed occur opinion organic evolution Origin of Species pangenesis panmixia parents particular peculiar plants possible present produced Professor Weismann's progeny prove question reason reflex action reflex mechanism regard remark restiform body reversal of selection sciatic nerve sexual selection somatogenetic specific characters statement structure sufficient suppose theory of heredity theory of natural tion transmission of acquired transmitted use-inheritance utility variations varieties Wallace Wallace's Weismann Weismann's theory
Page 319 - be indispensable for this act ; but as sutures occur in the skulls of young birds and reptiles, which have only to escape from a broken egg, we may infer that this structure has arisen from the laws of growth, and has been taken advantage of in the parturition of the higher animals
Page 27 - The special faculties we have been discussing clearly point to the existence in man of something which he has not derived from his animal progenitors—something which we may best refer to as being of a spiritual essence or nature, capable of progressive development under favourable conditions. On the hypothesis of this spiritual nature,
Page 4 - I have now recapitulated the facts and considerations which have thoroughly convinced me that species have been modified, during a long course of descent. This has been effected chiefly through the natural selection of numerous successive, slight,
Page 318 - In my opinion the greatest error which I have committed, has been not allowing sufficient weight to the direct action of the environment, ie food, climate, &c., independently of natural selection. Modifications thus caused, which are neither of advantage nor disadvantage to the modified
Page 187 - their true plumage after a few generations. An excellent observer (Mr. Hewitt) . . . found that he could not breed wild ducks true for more than five or six generations, as they proved so much less beautiful. The white collar round the neck of the mallard became broader and more irregular, and white feathers appeared in the duckling's wings
Page 321 - I fully admit that many structures are now of no use to their possessors, and may never have been of any use to their progenitors; but this does not prove that they were formed solely for beauty or variety. No doubt the definite action of changed conditions, and the various causes of
Page 326 - There can be little doubt that the tendency to vary in the same manner has often been so strong, that all individuals of the same species have been similarly modified without the aid of any form of
Page 182 - there can be little doubt that the tendency to vary in the same manner has often been so strong, that all individuals of the same species have been similarly modified without the aid of any form of selection 1
Page 326 - Or only a third, fifth, or tenth part of the individuals may have been thus affected, of which fact several instances could be given. Thus Graba estimates that about one-fifth of the guillemots in the Faroe Islands consist of a variety so well marked, that it was formerly ranked as a distinct species under the name of Uria lacrymans.
Page 327 - ignorant of the exciting cause of the above specified modifications; but if the unknown cause were to act almost uniformly for a length of time, we may infer that the result would be almost uniform; and in this case all the individuals of the species would be modified in the same manner*.