Biology, General and MedicalW. B. Saunders, 1910 - 440 עמודים |
מהדורות אחרות - הצג הכל
מונחים וביטויים נפוצים
activity amoeboid antigen appear bacteria become biophores blastula blood body buds cavity centrosome changes characters chemical chemotropic chromosomes cilia Class complexity conjugation containing corpuscles cytoplasm Darwin determinants differentiation digestive disease division ectoderm effected eggs embryo fertilization fibres filament flagella flowers fluid followed formation forms function gametes gemmules geotropic germ cells germ plasm germinal cells graft groups grow growth higher animals host hybrid hydra immunity increase individual insects irritability kidney kind known large numbers larvæ layer living substance living things matter Medical membrane ment microparasites modified molecules muscle nature nerve nervous system nuclear nucleus Nurses offspring organs ovum parasites parent peculiar physiological plants posterior primitive produced protoplasm pseudopods reactions regeneration reproduction segments serum sexual simple skin somatic species spermatocyte spermatozoa spores stage stimulation structure surface tail tentacles theory tion tissue toxin transplanted usually vacuoles vegetable vertebrates vessels worms yolk
קטעים בולטים
עמוד 265 - The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth. The green and budding twigs may represent existing species ; and those produced during each former year may represent the long succession of extinct species.
עמוד 264 - 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.
עמוד 361 - A propos of distempers, I am going to tell you a thing that I am sure will make you wish yourself here. The smallpox, so fatal, and so general amongst us, is here entirely harmless by the invention of ingrafting, which is the term they give it. There is a set of old women who make it their business to perform the operation every autumn, in the month of September, when the great heat is abated. People send to one another to know if any of their family has a mind to have the smallpox...
עמוד 263 - No one supposes that all the individuals of the same species are cast in the same actual mould.
עמוד 265 - As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever-branching and beautiful ramifications.