The descent of man and selection in relation to sex / by Charles Darwin.

  • Darwin, Charles, 1809-1882.
Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: The descent of man and selection in relation to sex / by Charles Darwin. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    conditions which now exist. Organs in this strictly rudimentary, but they are tending m this direction. SeJt organs, on L other hand, though -t Mly d7^^^^^ are of high service to their possessors, and are «^P^^ ^ development. Rudimentary organs are ^'^'^^''^^^l^^^^^ll^^^ this is partly inteUigible, as they are useless, or nearly useless, Ind consequently afe no longer subjected to natural selectio^ TheyTen become wholly suppressed. When this occi^s th 7 are nevertheless liable to occasional reappearance thiough xeversion-a circumstance well worthy of attention. tJc chief agents in causing organs to become rudimentary seem to have been disuse at that period of life when the jg^ is chiefly used (and this is generally ^-^^-^l^^'^''^^^ iBlieritance at a corresponding period of bfe. ^^^e term ^suse does not relate merely to the lessened action of muscls, but includes a diminished flow of blood to a part or Zan fiom being subjected to fewer alternations of pressure, or LTbecoiing in any way less habitually active. Kudmiente, however ray ?c ui- i/one sex of those parts which are normally Seseut iS^the other sex; and such rudiments, as we shall fereafter^ee, have often originated in a way distinct ^om those S referred to. In some cases, organs have been reduced by Z^^TZ.y^^X selection, from having become injurious to the Seeks under changed habits of Hfe. The process of reduction ?T)roLwroften aided thi-ough the two principles of compensa- iirand Lonomy of growth; but the later stages of reduction X ie has dLaU that can faii-ly be attributed to it and l:ngt he effected by theeconom^^^^^^ S^esS^oTa^ir^^^^^^^ play, IS peihaps ^^^^^^wL^^ of rudimentary organs —dld^^^^^^ in 3uy former wor^^ I need nVSrS%Tri^s — have been observed in many paS oftSe human body- and not a few muscles, which ai-e Zoolog. Soc- 1869. vol. vu. p 1)2 t petit.'' Another Variation ot Animals and nnes .n |^^.^^ posteric^,r, Plants under Domestication vol K f;;'^'^^;;^^,,, ue absent in the pp. 317 and 397 See also Ougm -j;^;;\,>p^^,, time to tin^c ot Species,' oth ed.t V-^J^- . ^ ^r loss rudimentary con- 2» For instance la. Kicnaid ^.u nales des Sciences Nat.. 3rd senos, dition.