Biology, General and MedicalW. B. Saunders, 1920 - 465 עמודים |
מהדורות אחרות - הצג הכל
מונחים וביטויים נפוצים
activity antigen appear bacteria become biophores blastula blood body buds cavity changes characters chemical chemotropic chromosomes cilia Class complexity conjugation containing corpuscles cytoplasm Darwin determinants differentiation digestive disease division ectoderm effect eggs embryo female fertilized fibres flagella flowers fluid followed formation function gametes gemmules geotropic germ cells germ plasm germinal cells graft groups grow growth higher animals host hybrid hydra immunity increase individual insects irritability kind known larvæ layer living substance living things male manifestations ment microparasites mitosis modified molecules muscle nature nervous system nuclear nucleus number of chromosomes nutrition offspring organisms ovum parasites parent peculiar physiological plants primitive produced protoplasm protozoa pseudopods reactions reflex regeneration reproduction segments separate serum sexual simple skin somatic species spermatocytes spermatozoa spores stage stimulation structure surface tail takes place tentacles theory tion tissue toxin transplanted usually vacuoles vegetable vertebrates vessels worms yolk
קטעים בולטים
עמוד 293 - 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 291 - This principle of preservation, or the survival of the fittest, I have called natural selection. It leads to the improvement of each creature in relation to its organic and inorganic conditions of life; and consequently, in most cases, to what must be regarded as an advance in organization.
עמוד 391 - 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 290 - No one supposes that all the individuals of the same species are cast in the same actual mould.
עמוד 293 - 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.
עמוד 391 - People send to one another to know if any of their family has a mind to have the smallpox: they make parties for this purpose and when they are met (commonly fifteen or sixteen together), the old woman comes with a nutshell full of the matter of the best sort of smallpox and asks what vein you please to have opened.
עמוד 391 - She immediately rips open that you offer to her with a large needle (which gives you no more pain than a common scratch), and puts into the vein as much...
עמוד 293 - ... of the former and present buds by ramifying branches may well represent the classification of all extinct and living species in groups subordinate to groups. Of the many twigs which flourished when the tree was a mere bush, only two or three, now grown into great branches, yet survive and...
עמוד 291 - If under changing conditions of life organic beings present individual differences in almost every part of their structure, and this cannot be disputed ; if there be, owing to their geometrical rate of increase, a severe struggle for life at some age, season, or year, and this certainly cannot...
עמוד 293 - The limbs divided into great branches, and these into lesser and lesser branches, were themselves once, when the tree was young, budding twigs; and this connexion of the former and present buds by ramifying branches may well represent the classification of all extinct and living species in groups subordinate to groups.