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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 external 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 physiological plants posterior primitive produced protoplasm pseudopods reactions regeneration reproductive 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
Popular passages
Page 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.
Page 2 - Nervous and Mental Diseases. By ARCHIBALD CHURCH, MD, Professor of Nervous and Mental Diseases...
Page 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.
Page 361 - 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...
Page 263 - No one supposes that all the individuals of the same species are cast in the same actual mould.