Spores of Chaetomium globosum have been subjected to monochromatic ultra-violet irradiation and colonies have been grown from single spores which were irradiated dry. Special attention bas been given to experiments in which The mercury lines at 265 m^u, 313 m^u, and 334 m^ were used. In all these cases many saltants wore produced as tbe result of the treatment of the spores. The primary object of the investigation was to observe any selective appearance of saltants at different wavelengths. Evidence for such a selective effect bas been given by one of ns, McAulay (1938") and the present experiments were made with more rpfined methods to obtaiii further information on this question, A very marked selective effect was found in which a certain easily recognized type of change was produced in large numbers of colonies grown from spores irradiated by short wavelengths, but in a very few irradiated by long wavelengths. This cbann'e is more in the nature of a growth modification than of a saltant, A part of the colony is normal but a sector appears whose vertex usually is not at the centre of the circular growing colony. Tbe sector is nearly clear of aerial mycelium and is frequently edged with dense brown in the substratum, Tbe aerial mycelium is often dense at the edge of thp sector and may form white knots. The modification has been designated by the letter "K."There is a particular feature of interest about the K type. The colony, grown from a single spore, comprises distinct parts eacb with quite different characteristics. It would appear tbat the mycelium growing from the single spores is tinstable in the sense that a colony derived from it may have two quite distinct forms.On several occasions tbe same single spore gave rise to three or more types, normal, K and a saltant (Fig, 2, No. 6),A very large number of saltant types is produced in Ch/ietomium glohosum by irradiation with wavelengths over the range 230 ma to 834 m/i. The percentage of colonies saltating is roughly constant over this range provided the energy per sq, cm. applied to the spore is a constant proportion of the lethal dose, in striking contrast to the "K" growth modification which appears selectively at short wavelengths. EXPERIMENTAL METHOD,The monochromator used in these experiments was constructed in the laboratory, and has been described by McAulay and Taylor (1939), A 125 watt mercury discharge lamp, a commercial unit with outer envelope removed, was used as a source of ultra-volet light.Spores were carefully spread on a eoverslip in a narrow are within the limits of thp wavelengths and separated from one another RO that all would have an equal opportunity of being irradiated. The spectrum was focussed on the spores by fluorescence of an underlying uranium 1 The funds required for thia work came from the Commonwealth Research Grant to the University.

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Lethal and quasi-lethal effects produced by monochromatic ultra-violet irradiation of biological material representing the phyla Bacteria, Fungi, Angiospermae, Protozoa and Arthropoda have been observed and recorded over a range of wavelengths from 254 to 365 mµ. Although the materials represent high and low forms in both vegetable and animal kingdoms, there is a striking similarity in their behaviour. There is a sudden increase in the lethal effect between 313 and 297 mµ, in every case. Although the curves connecting lethal dose with wave-length are closely similar in all cases, the absolute magnitudes of doses are widely different. The ratio of lethal doses for different material may be as high as two hundred to one at corresponding wave-lengths. The ratio of the greatest to the least dose recorded is of the order of a million to one. Tables and curves are given recording lethal and quasi-lethal doses for the different materials at different wave-lengths, and brief accounts of the conditions in which the experiments were conducted are given in the text. An interesting correlation is exhibited between the form of the lethal dose curves and the ultra-violet radiation in daylight.

I.-General.Whenever hydrogen overpotential occurs a t a cathode there must be some transition layer between the electrode surface and the electrolyte, where hydrogen exists in a condition whose free energy is greater than that of the gaseous hydrogen into which it passes. Even if the overpotential is believed to be the result of a resistant film this point of view is still applicable, the additional free energy in this case being the electrical energy between the plates of a condenser.The experiments described below seem to show th at this layer has many of the properties of a skin or film, and it will be referred to in the future as a film, without any significance being attached to the term besides that deduced in the course of the discussion. The experiments to be described were undertaken with the object of investi gating the nature and properties of this film, and consist mainly of simultaneous observations of the single electrode potential and the surface tension under varying conditions, a t a mercury cathode at which hydrogen is being evolved. These observations were made with a pure acid electrolyte and also with metal ions in solution with different current densities.The results obtained indicate that a film of high surface tension must form over the mercury surface before hydrogen can be liberated, and that this film persists after the current depositing the hydrogen is stopped and the overpotential has disappeared, provided that the electrolyte is of pure acid. The presence in the electrolyte of metal ions less noble than copper does not hinder the pro duction of the film nor destroy it when produced, but the presence of metal ions more noble than copper does prevent the formation of the film at low current densities and destroys it instantly on open circuit.The indication is that overpotential is a secondary effect caused by a tangible film hindering the transformation of hydrogen ions into gaseous hydrogen.

494by operators which satisfy the condition, P2 = P. The general principles of the representation of quantum states and physical variables by sectors and matrices in Hilbertian space can then be deduced from two physical hypotheses:-' ( a)th at (under specified conditions) there is a definite probability for the transition from the state represented by P to the state represented by Q.(6) th at this probability is the same for the transitions P -> Q and Q -> pThe association of congruent transformations with unitary operators leads to the theory of dynamically conjugate variables, and completes the theory of the " effective " value of a variable, averaged over all systems in a definite state. Metal electrodes immersed in air free solutions of KC1 were found to come to a definite reproducible potential. From the Nernst expression, this potential corresponds to a certain concentration in the solution of the ion of the electrode metal. Chemical analysis showed th a t the concentration that actually exists in the bulk of the solution is much smaller than th at deduced from the potential, even after electrode and solution have been in contact for weeks. A. L. McAulay and E. C. R. Spooner. A Unique Electrode PotentialIt was felt th a t a knowledge of the cause of this definite potential was fundamental to the general investigation of the potentials of metals in solutions of varying aeration, pn , and salt concentration, a subject of great practical importance which is at present in rather an indefinite and unsatisfactory condition.Work was undertaken with a view to obtaining information about the potentials of metals immersed in air-free solutions containing few of their own ions. In most of the experiments cadmium was used as an electrode, but check experiments have been made using other metals.The results disclose a single potential to which a metal tends to come, and leads to a theoiy for the mechanism which produces this. Further work was done on solutions which had been aerated.