Abstract
LONDON. Royal Society, November 2.— Sir Archibald Geikie, K.C.B., president, in the chair.—Sir W. de W. Abney: Colour-blindness and the trichromatic theory of colour-vision. Part iii.—Incomplete colour-blindness. The first part of the paper shows how, if an equation be formed by rays in known position in the spectrum to match a white, by normal vision and by the colour-blind, the two can be compared together without special reference to the luminosity of the matched white. The luminosities of all the rays are known in the one case, and only two in the second, and from the two matches the unknown deficiency of colour sensation can be calculated. Owing to the fact that large quantities of their white can be mixed with the colours without being detected by those incompletely colourblind who have a small factor for one of their sensations, a very false interpretation of their colour-blindness might be arrived at by the method described above. If, however, the luminosity of the composite white and the matched white be carefully equalised, a full determination of the colour deficiency can be arrived at by treating the equation somewhat in the manner described in part ii. of this same subject, when a true result is obtained. The latter part of the paper dealt with colour equations made from the rotation of discs; and it is shown that trustworthy results can be obtained from their use so long as the sensations stimulated by the pigments in the light in which they are viewed are known in amount. The method of ascertaining the sensation composition of the pigments, and of the light used for their illumination, is described. When once these are known, no further appeal to the spectrum is required. The author recommends the use of a white light passing through a yellow substance, such as chromate of potash solution, as a viewing light, in which only the red and green pigments are required in the inner disc, the blue not being wanted. The “grey” match becomes thus much brighter and is easier to read.—H. R. A. Mai lock: Note on the iridescent colours of birds and insects. In this note reasons are given for the view that certain forms of brilliant coloration which occur in the feathers of birds and in the scales and integuments of insects are due to interference, and are of the nature of the colours of thin plates. Walter, in 1895, in Germany, and quite recently Michelson in America, have written on this subject, and, basing their opinions on the behaviour of polarised light when reflected from the colour-producing surfaces, conclude that the colours are due to selective absorption and reflection, and are akin to those reflected from certain anilin dyes and from metals. The reasons against this view and in favour of interference are (1) that when any of these natural colour-producing structures are penetrated by a fluid having the same refractive index as that of the material of which the structure is composed, the colour disappears; (2) when the refractive index of the fluid is less, the colour does not disappear altogether, but changes towards the red; (3) (which is perhaps the most important) under mechanical pressure the colours first change towards the red and then (as the pressure increases) disappear. These results are what might be expected from a structure which produces interference, and it is difficult to reconcile them with any other hypolhesis. The note is founded on observations, extending over many years, on examples of this class of colour production taken from a considerable number of orders and genera, both of birds and insects, and the methods of examination employed are shortly described.—K. R. Lewi?: The behaviour of the infusorian micronucleus in regeneration. When Stylonychia mytilus is cut in two, so that each merozoon receives one member of the meganucleus and one micronucleus, both fragments exhibit in favourable circumstances complete regeneration. This involves segmentation of the meganuclear member and division of the micronucleus. If a portion of the cytoplasm be removed from the hind end of the animal without disturbing the nuclei, there may occur during regeneration a division of one, usually the posterior, micro-nucleus. The result is to furnish the regenerated infusorian with three micronuclei instead of two, i.e. the division does not restore, but actually disturbs, the nuclear relations characteristic of the race. When the regenerated individual proceeds to fission, all three micronuclei divide. That an extra division can be introduced into the normal cycle of mitoses shows that the organella is in a fit state to divide before the whole animal is ready for spontaneous fission; that the supernumerary mitosis occurs during regeneration suggests that the stimulus causing the micro-nucleus to divide may be the condition of the surrounding cytoplasm which obtains during the constructive activities of regeneration. The cases in which regeneration occurs without either of the micronuclei dividing can be supposed to be those in which either the micronuclei were not ripe for mitosis or the stimulus was not sufficiently intense to evoke a division-by reason, e.g., of regeneration occurring slowly, with no great intensity of constructive processes at any time. At the normal fission of the animal, when all the micronuclei present divide, there is a general formation of new parts quite comparable with the localised activity in regeneration, and accomplished, it is natural to suppose, with much the same condition of the cytoplasm. The normally occurring mitoses, and those taking place during regeneration, can thus be brought under one point of view.—A. F. Hayden and W. P. Morgan: An inquiry into the influence of the constituents of a bacterial emulsion on the opsonic index. These experiments, so far as they have gone, show that in the technique of the estimation of the tubercle opsonic index the quantity and character of the contents of the bacterial emulsion must be taken into account, and that the chief factor influencing the estimation is the finely ground bacterial detritus resulting from the process of triturating the dried culture of the bacillus.—Colonel Sir David Bruce: The morphology of Trypanosoma gambiense (Dutton).—A. H. Caulfeild: (1) Factors in the interpretation of the inhibitive and fixation serum reactions in pulmonary tuberculosis; (2) preliminary report upon the injection of rabbits with protein-free (tuberculo-) antigen and antigen-serum mixtures.
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Societies and Academies . Nature 88, 66–67 (1911). https://doi.org/10.1038/088066a0
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DOI: https://doi.org/10.1038/088066a0