| 释义 |
saltation|sælˈteɪʃən|
[ad. L. saltātiōn-em, n. of action f. saltāre to saltate.]
1. a. Leaping, bounding, or jumping; a leap.
1646Sir T. Browne Pseud. Ep. v. iii. 236 Locusts..being ordained for saltation, their hinder legs doe far exceed the other. 1710T. Fuller Pharm. Extemp. 129 Those odd Epileptic Saltations called St. Vitus's Dance. 1834McMurtrie Cuvier's Anim. Kingd. 396 The posterior legs of..the Orthoptera, are remarkable for the largeness of their thighs, and for their spinous tibiæ, which are adapted for saltation. 1852Dana Crust. ii. 1062 The animal swims by saltations, with great agility. 1881Trans. Obstetr. Soc. XXII. 152 The conclusion one might arrive at from the violent saltation of the fœtus. 1883Pall Mall G. 11 Sept. 11/1 It is not every flea..that is gifted with the power of saltation. 1897Syd. Soc. Lex., Saltation... Especially applied to the leaping sometimes noticed in cases of chorea.
b. spec. Dancing; a dance.
1623Cockeram i, Saltation, dancing. 1656Blount Glossogr., Saltation, a dancing. 1685E. Brown Trav. 10 The old Pyrrhical Saltation, or Warlike way of Dancing. 1814Scott Wav. xxviii, Still keeping time to the music.., he..continued his saltation without..intermission. 1879M. E. Braddon Clov. Foot iv. 34 Her dancing was distinguished for its audacity rather than for high art. She was no follower of the Taglioni school of saltation. 1890Harper's Mag. Oct. 797/2 These spangled saltations.
c. fig. An abrupt movement, change, or transition.
1844Gladstone Glean. V. xviii. 94 He must substitute for the saltations by which he reaches his conclusions..the patient and measured march of thought. 1854Emerson Lett. & Soc. Aims i. (1875) 61 The number of successive saltations the nimble thought can make.
d. Physical Geogr. A mode of transport of hard particles over an uneven surface in a fluid stream (as a wind or river), in which they progress in leaps, and on falling to the surface either bounce up for another leap or impart their momentum to other particles which on rising are accelerated forward by the stream. Cf. saltate v. 2.
1908W. J. McGee in Bull. Geol. Soc. Amer. XIX. 199 Transportation may be regarded as the general movement of earth matter seaward by streams; it comprises carriage of material (a) in solution, (b) in suspension, and (c) in what may be denoted saltation. 1941R. A. Bagnold Physics of Blown Sand & Desert Dunes ii. 20, I shall use the name ‘saltation’ for the motion of sand in air, but without prejudice to the question of whether or not the mechanism which causes the grain to jump from the surface is the same in the two fluids. In air it is certainly the impact of a grain with the surface; but this is rarely so in water. 1962Read & Watson Introd. Geol. I. iv. 206 The mechanisms of transport in the sea are similar to those already described in connection with rivers, namely, suspension, rolling and saltation. 1977A. Hallam Planet Earth 50 The sand grains suspended in the air are the smaller ones, movement of larger particles being along the ground by saltation—by a series of jumps.
†2. spec. Pulsation or spurting forth (of blood).
1672Wiseman Treat. Wounds ii. ix. 64 If it [sc. the blood] flow..from the left side, we suppose it the Artery, you will discover it by its saltation and florid colour. 1752C. Smart Hop-Garden i. 146 His verdant blood In brisk saltation circulates and flows. 1767Gooch Treat. Wounds I. 87 When veins are wounded, the blood does not flow with that impetuosity and saltation, as when proceeding from an artery.
3. Biol.
a. A mutation, esp. one with marked effects on several characters.
The ‘saltations’ studied by de Vries (see quot. 1906) are now known to have been translocations, which in Œnothera with its unusual system of chromosomes lead to large phenotypic changes.
1870Huxley Lay Serm. xiii. 343 We greatly suspect..that she [sc. Nature] does make considerable jumps in the way of variation now and then, and that these saltations give rise to some of the gaps which appear to exist in the series of known forms. 1906Pop. Sci. Monthly June 485 The name ‘saltation’, or in recent years ‘mutation’, has been applied to extreme fluctuation, the immediate cause of which is unknown. Ibid., Experiments of Dr. Hugo de Vries on the saltations of the descendants of an American form of evening primrose. 1919Jrnl. Exper. Zool. XXVIII. 381 In our opinion, the attempted distinctions between ‘saltations’, ‘mutations’, and ‘variations of slight degree’ have led rather to confusion of thought than to clearer thinking. To us these are all a single class, ‘mutations’. 1930R. A. Fisher Genetical Theory Nat. Selection vii. 163 Unless such a resemblance formerly existed a gradual mimetic evolution is precluded, and we should be forced to admit that the mimetic females arose as sports or saltations totally unlike their mothers. Ibid. 164 A single saltation from a male of the same species. 1963E. Mayr Animal Species & Evolution xv. 435 The sudden origin of new species, new higher categories, or quite generally of new types by some sort of saltation has been termed macrogenesis.
b. Change of phenotype occurring within a fungal colony.
1922F. L. Stevens in Bull. Illinois Nat. Hist. Surv. XIV. v. 157 The existing differences in definition and usage of the term mutation, as also our very limited knowledge of cytological conditions in the genus Helminthosporium and our ignorance as to whether it has sexual stages, have led me to select the term saltation for the variations here discussed. 1926Ann. Bot. XL. 223 Changes of a more lasting nature may be conceived as arising gradually as a response or adaptation to certain growth conditions, or by sudden jumps. The latter type of phenomenon, which is known to occur in a considerable number of fungal genera,..is usually described as a ‘mutation’, or more conservatively as a saltation. 1940J. Ramsbottom in J. S. Huxley New Systematics 414 The morphological range is often so great that a single saltation will give what would be considered as a new species. 1978Nature 29 June 755/1 The common and poorly understood phenomenon of frequent somatic variation in certain supposedly haploid fungi (saltation) may perhaps be due to the loss of extra chromosomes that had been acquired previously.
Hence salˈtational a., of, pertaining to, or occurring by means of saltation.
1963E. Mayr Animal Species & Evolution xv. 435 The reorganization of the gene pool, required for successful speciation, is (except in the case of polyploidy) never saltational. Ibid. 437 Some saltational postulates are based on the assumption of essentially invariant evolutionary rates. 1978Sci. Amer. Sept. 41/1 Even T. H. Huxley..could not accept the gradual origin of higher types and new species; he proposed a saltational origin instead. |