Essays in scientific synthesis / by Eugenio Rignano.

  • Eugenio Rignano
Date:
[1918]
Catalogue details

Licence: In copyright

Credit: Essays in scientific synthesis / by Eugenio Rignano. Source: Wellcome Collection.

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    had been placed in it at first. And there are further instances of the kind.1 Now, it is interesting to note that the new con¬ ditions of the environment to which the animal be¬ comes gradually accustomed tend in time to become its optimum : “ Individual adaptation (e.g. to each change of saline density) is effected according to the law by which the conditions of density under which an individual is constrained to live tend in time to become the optimum conditions for that individual/’ 2 The fact may be verified even in plant organisms. Plasmodia of the Myxomycetes, which would die if suddenly plunged into i or 2 per cent, solutions of glucose, and which draw back from solutions of I or I per cent., may yet gradually become so accustomed to 2 per cent, solutions that they finally show by their behaviour ” that they prefer the new environment to the original one without glucose. 3 The diatom Navicula brevis normally shuns even the weakest light, and tries to hide itself in the darkest part of the drop of water in which it is being observed. But a culture which is placed in the bright light of a window for a couple of weeks exhibits exactly the opposite tendency. It moves into the brightest part 1 Cf. C. B. Davenport and W. E. Castle, On the Acclimatisation of Organisms to High Temperatures. “ Archi v f. Entw. Mech. d. Organis- men,” II. Band, ii. Heft, July 1895 ; C. B. Davenport and H. V. Neal, On the Acclimatisation of Organisms to Poisonous Chemical Substances, ibid.) II. Band, iv. Heft, January 1896. 2 Davenport and Castle, ibid., p. 241.' 3 E. Stahl, Zur Biologie der Mymmycet&n, i( Botaniche Zeitung,” March 7, 14, 21, 1884, p. 166.
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