Societies and Academies

Abstract

EDINBURGH. Royal Society, June 19.—Prof. Bower, F.R.S., vice-president, in the chair.—M. Jules Cardot: Les Mousses de 1'Expédition nationale antarctique ecossaise. These were collected in various localities visited, and included a number of new species and genera.—Dr. J. Aitken, F.R.S.: Some nuclei of cloudy condensation. Some years previously the author, when enumerating the dust particles in the air at certain regions of the West Highlands remote from centres of population, had noticed from time to time a sudden, and at first inexplicable, increase in the number of dust particles. A recent study of the phenomenon had shown that the increase was due to the sunning of the material on the foreshore of neighbouring islands and coasts. The paper discussed the probable causes of this production of dust particles, and described a number of experiments on the direct effect of sunlight upon various substances.—Dr. A. A. Lawson: Nuclear osmosis as a factor in the mechanism of mitosis. A study of the spore mother-cells of Disporum, Gladiolus, Yucca and Hedera, and the vegetative cells in the root tip of Allium, has revealed a series of stages in the development of the mitolic spindle which has hitherto been overlooked. They are important and critical stages concerning the fate of the nuclear membrane, and are to be found in the early pro-phase, preceding the organisation of the equatorial plate. Contrary to the generally accepted view, it has been found that the nuclear membrane does not break down during spindle formation, but behaves as a permeable plasmatic membrane should behave under varying osmotic conditions. The interpretation of these stages throws an entirely new light on the problem of the “mechanism of mitosis,” and necessitates a revision of the accepted views of nuclear phenomena. It goes to prove that osmotic conditions are active factors in the formation of the acromatic spindle.— Dr. A. G. M'Kendrick and Dr. Kesava Pai: The rate of multiplication of micro-organisms: a mathematical study. Assuming the law that the rate of increase of fast-growing organisms is proportional to the number of organisms present and to the concentration of the foodstuff, the authors express this in the mathematical form dy/dt=by(a—y). At the beginning, y is small compared with a, so that the constant ab is equal to the rate of change of log y. From the graph which gives log y in terms of time, the value of ab may be readily obtained, and from the indications of the experiments the limit a towards which y tends may be inferred. The quantity also gives by a simple calculation the period of a generation. The numbers calculated from the integrated expression were found to be in good agreement with the numbers obtained by direct measurement.