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International audience; The largest products of magmatic activity on Earth, the great bodies of granite and their corresponding large eruptions, have a dual nature: homogeneity at the large scale and spatial and temporal heterogeneity at the small scale1-4. This duality calls for amechanism that selectively removes the large-scale heterogeneities associated with the incremental assembly4 of these magmatic systems and yet occurs rapidly despite crystal-rich, viscous conditions seemingly resistant to mixing2,5. Here we show that a simple dynamic template can unify a wide range of apparently contradictory observations from both large plutonic bodies and volcanic systems by a mechanism of rapid remobilization (unzipping) of highly viscous crystalrich mushes. We demonstrate that this remobilization can lead to rapid overturn and produce the observed juxtaposition ofmagmatic materials with very disparate ages and complex chemical zoning. What distinguishes our model is the recognition that the process has two stages. Initially, a stiff mushy magma is reheated from below, producing a reduction in crystallinity that leads to the growth of a subjacent buoyant mobile layer. When the thickening mobile layer becomes sufficiently buoyant, it penetrates the overlying viscous mushy magma. This second stage rapidly exports homogenized material from the lower mobile layer to the top of the system, and leads to partial overturn within the viscous mush itself as an additional mechanism of mixing. Model outputs illustrate that unzipping can rapidly produce large amounts of mobile magma available for eruption. The agreement between calculated and observed unzipping rates for historical eruptions at Pinatubo and at Montserrat demonstrates the general applicability of the model. This mechanism furthers our understanding of both the formation of periodically homogenized plutons (crust building) and of ignimbrites by large eruptions.

Mehl announced in 19451 that by the use of ethylene glycol an alkaline copper reagent could be prepared in which copper, besides not being precipitated, could give the biuret reaction. At the high proportion in which glycol enters into Mehl's reagent, the presence of reducing impurities made it necessary to prepare the reagent in two stages, heating in order to speed up the reaction, and filtering in order to remove the precipitated copper. Nevertheless, the presence of the colour of the alkaline copper reagent causes the reaction to depart considerably from Beer's law; Mehl deduces from a spectrophotometric analysis that, starting from the 750 mµ and 545 mµ absorptions, the quantity of proteins present can be approximately calculated.

Rigor cross-bridges show two conformations paired within each 38.7-nm axial repeat. The two forms may express two stages of the cross-bridge cycle during contraction. Differing numbers of myosin heads per cross-bridge and associated helical changes in the thin filament distinguish the two forms and suggest that both myosin heads usually bind to a single thin filament.

Evidence is presented which strongly suggests that most of the southern Red Sea is underlain by oceanic crust which evolved in two stages, the first from about 41 to 34 million years ago and the second from about 4 to 5 million years ago to the present day.

The aggregation of human blood platelets is stimulated by ADP and other materials, and is known to take place in two stages. Studies with chlorpromazine, imipramine and related compounds indicate that they affect the second stage

IN the present volume Mr. Romanes redeems a part of the promise which he gave us in his “Animal Intelligence.” He traces in its main outlines the development of mind in the lower animals. The other part of the promise, to follow the course of mental development in man, will be fulfilled in another work. We think it well that the author has thus divided his task. Each division is of sufficient magnitude to require a separate volume; and though as an evolutionist Mr. Romanes would of course maintain the continuity and identity of the process of mental evolution from its first obscure manifestations in the lower grades of animals up to its highest present point of attainment in civilised man, he would probably allow that the two stages of the process, the sub-human and the human, are sufficiently differenced by the difference in the degree of complexity of the factors involved. To this it may be added that the detailed study of each of these two stages of mental life requires a body of knowledge of its own, a special modification of psychological method, and a particular kind of psychological interest. Mental Evolution in Animals. By G. J. Romanes, &c. With a Posthumous Essay on Instinct, by Charles Darwin. (London: C. Kegan Paul & Co., 1883.)

The Red Sea forks northwards into the Suez Graben and the Dead Sea-Arava Rift (Fig. 1). The southern part of the latter, about 165 km long, is occupied by the Gulf of Aqaba (Elat). A sinistral strike-slip movement of about 107 km which was suggested to have occurred along the Dead Sea–Arava Rift1–3 is related to the opening of the Red Sea proper1,4–6. The opening of the Red Sea was considered to have taken place in two stages. The various dates proposed for the first movement are: from 41 to 34 Myr (ref. 5), from 29 to 24 Myr (ref. 7) and from 20 Myr onwards6. The second movement is generally dated from 4–5 Myr to Recent. Garfunkel and Bartov8 claimed that the rifting in the Gulf of Suez was well under way in the span of the late Oligocene to early Miocene (30–20 Myr) and that a drastic change in the tectonic regime occurred in the middle Miocene (15–16 Myr). We suggest here, however, that the opening of the Red Sea is younger than 19–22 Myr.

THE effects of a toxic be substance upon a cell are not instantances. There is always a course of events leading up to the changes, reversible or otherwise, which are imposed upon the organisation of the normal cell by a toxic substance. The action generally occurs in two stages. In the first stage, the toxic fact or reacts with certain components of the cell. In the second, and from some points of view more important stage, the organisation of the cell changes because of the impairment of function of the components directly affected by the toxic factor. The second stage does not, of course, occur until the activities of the cell involve the operation of the components of which the function is impaired ; and so it may readily happen that only when the cell is disturbed from a state of rest does the action of a toxic substance become apparent or lethal.

A RESPONSE that has waned as a result of continuous stimulation without reinforcement may reappear when the stimulus is presented on another occasion: habituation, as defined by Thorpe1, is “relatively permanent” but not complete. The extent of recovery of the response will clearly be a function of the length of time between presentations, but several workers, notably Hinde2,3, have shown that the relation between recovery and rest interval is not a simple one. Recovery seems to occur in at least two stages, possibly reflecting the existence of separate underlying physical processes. Some recent experiments with the cuttlefish, described here, have revealed a two-stage recovery with much sharper separation than has been found previously.

THE thermal decomposition of dolomite has repeatedly been investigated; but the mechanism of this reaction still remains obscure. Some authors suppose that solid solutions of carbonates are formed during decomposition1, others assume primary dissociation into separate carbonates2 or into oxides3 of magnesium and calcium. However, the fact that thermal decomposition takes place in the two stages (i) and (ii) has been generally established.

Lord and Potter have reported1 that they could not obtain preparations of Tenebrio molitor larvae or Tribolium castaneum adults which could hydrolyse acetyleholine. This failure is surprising in view of the supposed ubiquity of cholinesterase “in conductive tissue throughout the whole animal kingdom”2, and is of importance because of its bearing on the question of the mode of action of organo-phosphorus insecticides. Since both insects are killed by low concentrations of tetraethyl pyrophosphate (TEPP), Lord and Potter's observations would indicate that the significance of its anti-cholinesterase effect is not as great as had been thought3. Although the authors stated that “no persistent attempt was made to prepare an extract hydrolysing ACh”, their work has been taken to show4 the absence of cholinesterase in these insects. In their principal preparation, the supernatant from their homogenates was treated with half its volume of ethyl alcohol. The inability of the resultant solution to hydrolyse acetylcholine is not surprising in view of the anti-cholinesterase activity of ethyl alcohol5. Furthermore, the brei was centrifuged at two stages, and the centrifugates rejected; Babers and Pratt6 have shown that, in the honey-bee, five-sixths of the cholinesterase is in the centrifugate of whole brei.

Although the exact role of calcium in the complex mechanism of blood coagulation is still in some dispute, it is certain that it is a basic element in some of the interactions taking place between the various blood-clotting factors which finally lead to the formation of the prothrombin-converting factor, plasma thromboplastin1. Recently, we2 described an ether-precipitation method for the separation of the latter. Further work, reported herein, on the relation between this important blood-clotting factor and calcium has revealed the presence of two stages in the production of a fully active plasma thromboplastin.

A WETTING liquid makes a zero contact angle to a solid, and a drop will spread completely over the surface. There are two stages in the spreading process12. Initially, the advancing front is pushed from behind by the hydrostatic head of the liquid. As the drop thins out this becomes unimportant and the front is pulled along by the unbalanced surface forces near the perimeter. The shape of the advancing front is not easy to observe without special lighting. In addition, for most liquids it cannot be seen unless precautions are taken to minimise evaporation. I report here microscopic observations which show that the advancing front has a remarkable structure. The moving front does not retain the shape of the original drop. Instead, depending on the liquid, it either assumes a scalloped periodic structure or else moves by a series of random advances, resembling the locomotion of an amoeba, but still with some approximate periodicity.

THE phenomena very briefly outlined in this communication are the results of a planned series of investigations undertaken to clarify certain observations the significance of which was not at first very evident. Only certain (human) subjects are sensitive to injections of the materials referred to, and it is with regard to such ‘sensitives’ that the following account applies.

THE role of pigment migration in light–dark adaptation of the eyes of nocturnal moths has long interested investigators1,2. Efforts have been made to find out what part pigment migration plays in the behavioural changes associated with light–dark adaptation3, and in the phenomenon called ‘glow’4. Recently, it has been reported that adaptation in nocturnal moths occurs in two stages, the first of which is not accompanied by pigment migration5. The discovery that variations can occur in the light-threshold of a dark-adapted compound eye with practically no change in the glow area6 is further evidence of the independence of adaptation and pigment position.

OF the various parasitic rusts of the coniferous trees now under investigation, one which baffled us for many years and has been a serious pest of Pinus longifolia Roxb., the Chir pine, in north and northwestern India, has been recently worked out. The aecidial stage (Fig. 1) which was formerly known as Peridermium orientalis Cooke, and also as Peridermium complanatum var. corticola Barclay, has been recently redescribed as Penidermium himalayense Bagchee (Indian Forest Records, Botany Series, Vol.14, Part 3, 1929). This fungus has caused much mortality every year not only in the plantations of Almora (Fig. 2) and Naini Tal, but has also impeded natural regeneration in Kumaon and Garwhal Himalayas, where the young pine stands appear to be doomed to eventual extermination. The infection and mortality is very severe in young crops of pine up to the advanced sapling stage, but the poles and mature trees are apparently safe from attack. The Cronartium stage has been discovered on Swertia species, of which S. alata Royle, S. angustifolia Ham., S. cordata Wall., appear to be very susceptible to this rust. The biological relationship of the two stages has been proved recently by cross-inoculation experiments. The detailed report of this investigation will appear in a subsequent issue of Indian Forest Records.

PREVIOUS investigations of the oxidation of thiosulphate by the autotrophic micro-organism Thiobacillus thioparus have not led to uniform results. According to Starkey1, thiosulphate is oxidized directly to sulphur and sulphate, and Parker and Prisk2 have also come to a similar conclusion. On the other hand, Vishniac claims that the oxidation of thiosulphate by Th. thioparusoccurs in two stages: the first is the complete oxidation of the substrate to tetrathionate and the second the oxidation of the tetrathionate3. The results of Pratt's investigations4 also suggest the possibility of the appearance of tetrathionate during the oxidation of thiosulphate by Th. thioparus. Pratt showed that in the medium in which Th. thioparus was growing there was an accumulation of some substance, presumably tetrathionate, giving a positive Folin–Ciocalteu reaction.

PLASMA kinin1 (originally named “pain-producing substance”2) is a pain-producing and smooth muscle-contracting polypeptide which can be released from human blood plasma in a number of ways, including contact with glass and some other surfaces. The mechanism of kinin release by contact has been resolved into two stages : in the first, ‘contact factor’ is formed from its precursor (‘component A’) ; in the second ‘contact factor’ reacts with another constituent (‘component B’)1,3.

THE first step in the transfer of iron from the plasma iron-carrying protein, transferrin, to reticulocytes and probably to other erythropoietic cells, is the binding of transferrin to the cells1,2. After release, the iron from transferrin enters the haem synthesis pathway, while the transferrin is released from the cell. The transferrin binding occurs in two stages, an initial rapid, temperature insensitive stage, probably adsorption to the cell membrane, and a slower temperature dependent stage which results in a firmer union of the transferrin to the cell3. Little is known about the nature or the site of transferrin binding to reticulocytes. We report here that transferrin actually penetrates into the interior of the cell.

RESAZURIN was discovered by Weselsky1, and first used by Pesch and Simmert in 19292 for estimating the bacterial content of milk. It has lately been extensively used in Great Britain as a basis for a number of tests for the hygienic quality of milk3,4. Reduction takes place in two stages

IN recent years there has been an increasing interest in the role of leuco-anthocyanins as possible precursors of anthocyanins in vivo. Evidence for and against this hypothesis has been presented by many workers, and reviewed by Alston1. In the course of the isolation and identification of the anthocyanin pigments of sour cherries2 and sweet cherries3 in this Laboratory, these fruits at two stages of maturity were examined for the occurrence of leuco-anthocyanins. Evidence was found for the presence of the leuco-anthocyanin related to cyanidin, which is also the single nucleus for the anthocyanin pigments in cherries2,3.

IT has been assumed by Apitz1 that the transition of fibrinogen to fibrin is not a simple reaction, but takes place in two stages. The primary product should be a soluble substance, less stable than fibrinogen, which he called profibrin. By suitable choice of the composition of the electrolytes of the medium, we succeeded in studying the two phases of the reaction separately; thus we obtained a substance which has a better-founded claim to the name profibrin.