bluuebunny/crossref_metadata_2025_split huggingface dataset:
COLEOPTERAN ASSOCIATIONS IN THE BRITISH ISLES DURING THE LATE QUATERNARY PERIOD
Authors: PEARSON R. G. 
Published: January 2008

Summary1. The fauna of the climatic optimum of the Eemian Interglacial period contained thermophilous species and as such indicates a climate at least as warm as that today.2. The Chelford fauna dating from ca. 57,000 years before the present is comparable to that of Finland and Soviet Karelia. An analysis of the Carabidae suggests that within Scandinavia it is comparable with that which occurs at the top of the regio quercina.3. The Upton Warren fauna contains stenothermal arctic and boreal species and one Uralian species. The Carabidae suggest a comparison with the regio coniferina in Scandinavia.4. The Fladbury fauna has a large number of stenothermal arctic and boreal species and the Carabidae suggest a comparison with the top of the regio betulina in Scandinavia.5. The Colney Heath fauna contains stenothermal and stenotopic arctic and boreal species. The Carabidae suggest a comparison with the regio coniferina in Scandinavia.6. The St Bees fauna only contains a few remains of stenothermal boreal species and there is a considerable change in the percentage representation of the dominant species within the deposit.7. The stenothermal arctic element largely disappeared from the lowland fauna in a period of some 1600 years during pollen zone I.8. The thermophilous species immigrated into north‐west Europe in some 3000 years between pollen zones III and VII.9. Heliophilous species are well represented in Full‐ and Late‐glacial deposits. Their present restricted distribution is the result of Post‐glacial afforestation.10. Halophilous species have undergone a restriction in their range comparable to that of the heliophilous species.11. It is possible that certain observed distributional anomalies previously thought to result from glacial survival and subsequent extension of range may be the result of Post‐glacial survival in areas where there was only limited afforestation.12. During the late Quaternary era the changes in the distribution of the beetles parallel those of the angiosperms and gymnosperms.13. In terms of the Full‐, Late‐ and Post‐glacial periods the terminocratic grouping includes boreo‐alpine, northern oceanic, eurythermal and heliophilous species. The mediocratic grouping includes southern continental and oceanic eurythermal species.
PHOSPHATES AS CRYSTAL POISONS OF CALCIFICATION
Authors: SIMKISS K. 
Published: January 2008

Summary1. A theory has been proposed by Neuman that some metabolites which contain phosphate groups can act in the body as crystal poisons and so influence the deposition of calcium salts in skeletal structures. This theory is explained and the evidence for it reviewed.2. A crystal poison is a compound which settles on the surface of a crystal and interferes with the continued formation of the crystal lattice. Thus crystal growth stops and the mother liquor may become supersaturated.3. The evidence in favour of the theory is considered, both for phosphatic skeletons such as bone and calcareous skeletons such as those found in many invertebrates.4. Many of the phosphate groups in metabolites can produce the inhibitory effect and it has been suggested that a phosphatase enzyme acts in destroying these crystal poisons by hydrolysing them at the site of mineralization.5. Pyrophosphates are effective crystal poisons at very great dilutions, and yet they have been shown to be present in ossifying bones and in the plasma and urine of mammals.6. Alkaline phosphatase is present during the formation of calcareous skeletons, but the explanation of the removal of a crystal poison by hydrolysis is complicated by the fact that orthophosphates also inhibit calcification.7. These data are discussed in relation to the physiology of calcification in animals with phosphatic and with calcareous skeletons and some of the implications of the theory are evaluated.
MICRO‐ORGANISMS and SOIL STRUCTURE
Authors: GRIFFITHS ELLIS 
Published: January 2008

Summary1. Experimental analysis of the influence of micro‐organisms on soil structure has been confined to aggregation, i.e. the formation of small clusters of soil particles which are resistant to the disintegrating action of water.2. Aggregation is influenced by the mineral constituents of the soil, notably clay, but organic matter is considered to be most important.3. Decomposition of organic matter regularly leads to increased aggregation in non‐sterile soils. Under sterile conditions (i.e. in the absence of micro‐organisms) no increase in aggregation is observed, so that it is evident that micro‐organisms are implicated in this process.4. Investigations of the role of micro‐organisms have been concerned with two possible effects: (1) the action of filamentous organisms (particularly fungi) in mechanically entangling soil particles to form stable aggregates, and (2) the action of products of micro‐organisms (of all groups) which may cement soil particles together.5. In most soils the mycelium of filamentous organisms (fungi and actinomycetes) is only present for relatively short periods so that aggregation produced by them tends to be ephemeral. In sandy soils, however, mycelium appears to be more persistent and hence of greater significance. Since fungi are commonly associated with the early stages of decomposition of plant remains, it is suggested that they may also be important in situations where plant residues are regularly being added to the soil, e.g. grassland and forest.6. Of the many compounds produced by micro‐organisms, most attention has been given to extracellular polysaccharides. These are produced by many soil organisms and can be shown to be effective aggregating agents. Compounds of similar character have been demonstrated in natural soils but satisfactory methods for their quantitative estimation have not been developed. Consequently their contribution to aggregation cannot be accurately evaluated. Evidence so far presented, does, however, indicate that in many cultivated soils they make a considerable contribution.7. In old grassland and forest soils, extraction of polysaccharide by periodate oxidation appears to have little or no effect on aggregation and in these cases aggregation would seem to be due to other components of the soil organic matter. Although this may well be so, it is also suggested that the distribution pattern of organic materials in the soil may be an important contributory factor. Certain materials, e.g. lipids, though not effective as aggregating agents when mixed with the soil, increase stability when sprayed on the surface of unstable aggregates. The significance of such effects has not so far been critically examined.
THE RELATIONSHIP BETWEEN BLUE‐GREEN ALGAE AND BACTERIA
Authors: ECHLIN P. , MORRIS I. 
Published: January 2008

SummaryRecent studies of bacteria and blue‐green algae in the electron microscope have shown striking similarities in the basic cellular architecture of the two groups. This evidence has been presented in detail above and may be summarized as follows:(I) The cell envelope of blue‐green algae bears a superficial resemblance to the cell wall of bacteria, particularly to the Gram‐positive organisms. Like bacteria, blue‐green algae also possess a mucopeptide component as an important part of the cell wall. However, the composition of this mucopeptide component resembles more closely that of Gram‐negative bacteria, though more species of blue‐green algae need examination before the relationship can be established with any certainty.(2) The older distinction between the chromatophores of photosynthetic bacteria and the lamellae of blue‐green algae has been shown to be superficial. In both forms the essential feature of the photosynthetic apparatus is a pair of membranes enclosing a space; this may be large in bacterial chromatophores or small in ‘true’ lamellae. This basic structure is seen in higher plants where the lamellar systems are enclosed in a membrane‐bounded structure, the chloroplast. No such membrane isolates the photosynthetic machinery of bacteria and blue‐green algae.(3) No membrane isolates the nuclear material of blue‐green algae or bacteria. The nucleoplasm of these two groups is structurally similar and show the same morphological changes with variations of fixative treatment.(4) Both bacteria and blue‐green algae lack mitochondria, true vacuoles and an endoplasmic reticulum. Membranous structures (mesosomes) are widespread in bacteria and recently similar structures have been seen in blue‐green algae.(5) The nucleoplasm presumably divides by an amitotic process, as no stages of mitosis or meiosis have been observed in either group. The cell division in blue‐green algae shows a superficial resemblance to that of Gram‐positive bacteria.Recent observations on the cytoplasmic inclusions of the two groups have been presented above, but no pattern has yet emerged. The spores of the two groups have also been discussed and the little detailed observation available supports earlier suggestions of some important differences between the two groups.Bacteria and blue‐green algae also resemble each other and differ from other organisms in their method of ornithine biosynthesis, their apparent absence of sterols and their sensitivity to certain antibiotics.The evidence here summarized supports the suggestion that bacteria and blue‐green algae should be isolated in a group distinct from all other organisms. Two speculative aspects of the problem have been discussed: their evolutionary relationship with other organisms and with each other. With regard to the latter, it seems probable that bacteria and blue‐green algae arose from a common ancestor, since it is unlikely that so many features common to the cells of both groups arose independently more than once.
STRUCTURE AND FUNCTION OF MAMMALIAN TENDON
Authors: ELLIOTT D. H. 
Published: January 2008

Summary1. Tendons are a specialized form of connective tissue uniting muscle and bone and as such have functions essential to normal mobility.2. The structural unit of tendon is the fibre, up to 300 µ in diameter, consisting of fibrils of collagen, encircled by the anastomosing processes of fibroblasts. Fibres are arranged in fasciculi but may pass from one to another so that successive cross‐sections show slightly different appearances. Such interweaving ensures the equal distribution of muscular tension over the whole area of insertion, particularly where the movement of a joint alters the angle between tendon and bone.3. There are two hypotheses concerning the nature of the muscle‐tendon junction. First, the tension developed within a muscle fibre might be transmitted to the helical perisarcolemmal fibres of connective tissue surrounding its length and thence to the tendon, and secondly, and more probably, the tension might be transmitted directly from the end of the myofibrils to the interdigitating fibrils of the tendon. The interdependence of muscle and tendon is further illustrated by their longitudinal growth since the changing length of the muscle belly relative to the distance between the bony attachments determines the rate of growth and relative length of tendon.4. The orientation of fibrous tissue in the tendon supports the hypothesis of a mechanical influence upon tendon growth, but there is no strict relationship between muscle strength and tendon thickness and various muscles differ in the ratio of their total fascicular cross‐sectional area to tendon thickness. It would appear that this difference develops post‐natally and, since a red postural muscle has a relatively thick tendon, it has been suggested that the duration as well as the level of transmitted tension might influence the growth of collagen.5. Tendon thickness may increase proportionately with muscle cross‐sectional area in conditions which cause the muscle to hypertrophy, but when the muscle is de‐nervated or excised in the young animal growth of tendon thickness occurs in such a manner as to suggest that the growth of collagen is determined by the history of the total tension transmitted.6. The tendon has a tensile strength which is probably four times as great as the maximum tension that it has to transmit in vivo and an even greater margin of safety is present in penniform muscles which transmit less maximum isometric tetanic tension per unit fascicular cross‐sectional area than do fusiform muscles. Although the wave form seen on the surface of a tendon when at rest is eliminated by less than 10 % of the maximum tension which its muscle is liable to transmit, it is possible that the normal range of tensions transmitted in vivo might fall within that part of the stress‐strain curve where the tendon is still easily extensible.
ENVIRONMENTAL AND BIOCHEMICAL CONTROL OF STOMATAL MOVEMENT IN LEAVES
Authors: ZELITCH I. 
Published: January 2008

SummaryThe chloroplasts of guard cells are largely responsible for the response of stomata to light. The opening movement is probably associated with the synthesis of ATP by non‐cyclic photophosphorylation, and the obligatory fixation of carbon dioxide to produce glycolic acid. The oxidative metabolism of glycolic acid is related to ATP synthesis as well as to the possible formation of carbohydrate. In the absence of oxygen in the gas phase, stomata open poorly, and the synthesis of glycolic acid is also inhibited. α‐Hydroxysulphonates, which are inhibitors of glycolate oxidase, prevent stomatal opening in a competitive manner. High concentrations of carbon dioxide close stomata and inhibit the formation of glycolic acid, and the effect of high carbon dioxide on closing can be reversed by providing the tissue with glycolic acid.When leaf hydration is not limiting, raising the temperature in the environment causes an increase in the steady state of the stomatal aperture. There is little effect of temperature on the rate of closing in darkness, hence opening is the active process.A large number of chemical inhibitors were found to prevent opening, either by interfering with metabolic reactions in the guard cells concerned with the ‘pump’ responsible for the increased turgidity, or by acting on the membranes that serve as a ‘check valve’. Sodium azide is a substance which acts by both mechanisms, but the maximal effect occurs at different concentrations, and experiments with this inhibitor have shown that the opening and closing reactions operate independently.
STOMATAL RESPONSES TO ILLUMINATION
Authors: MEIDNER HANS , MANSFIELD T. A. 
Published: January 2008

Summary1. Stomata have been found to respond to small changes in carbon dioxide concentration within the leaf, and movements due to illumination, temperature, leaf‐water content, or metabolic inhibitors can be explained, at least in part, by their affecting the internal carbon dioxide concentration. This is confirmed by the fact that effects of such factors can be reversed experimentally by flushing the leaf with air of an appropriate carbon dioxide content. We conclude that changes in carbon dioxide concentration set in motion reactions affecting guard cell turgor relations (see 8 below).2. The photosynthetic production of carbohydrates, or of intermediates in their synthesis such as glycollic acid, does not seem to have any major effect on guard cell turgor, which can readily change in the absence of photosynthesis in darkness in response to different carbon dioxide concentrations. Factors which affect photo‐synthetic production ordinarily affect the internal carbon dioxide concentration and it is the latter which is more directly involved in changing guard cell turgor relations.3. In addition to the effects of environmental factors on carbon dioxide concentration, light (blue), temperature and leaf water content may also affect guard cells independently of carbon dioxide. Whether such effects are due to hydrolysis of starch or another polysaccharide, or to changes in permeability or quite another mechanism, is not known.4. As well as being effected by the environment, stomatal movements are under the control of endogenous rhythms in light and darkness. Rhythms can produce opening in darkness and partial closure in light, and hence can modify or overrule the response to external factors. However, the phase of the rhythm does come under the control of the environment through a low‐intensity light reaction sensitive to red and far‐red wavelengths. This light reaction is quite distinct from those directly concerned in the production of stomatal opening.5. Stomatal behaviour in cacti and other succulents is at first sight practically the opposite of that in other plants, in that they open at night and close during the day. We suggest that this type of behaviour may, however, be a relatively simple development from the normal pattern.6. Stimuli affecting the stomata can be transmitted within a leaf, or from one part of a plant to another. The mechanism of the transmission is not known, but it could be brought about by a chemical substance which is translocated.7. There is evidence that the processes of stomatal opening and closing are different in nature, and that one is not simply a reversal of the other. It is probable that an active (oxygen‐requiring) mechanism in involved in stomatal opening. Stomata come under the control of so many factors, both external and internal, that several processes are likely to contribute to the turgor changes which bring about their movements.8. The mechanism of carbon dioxide control over stomata is not known.
SELECTION, PREDICTION AND RESPONSE
Authors: LEE B. T. O. , PARSONS P. A. 
Published: January 2008

Summary1. The biometric approach to selection experiments has been outlined, and found to be rather deficient because it is based on excessively restrictive models which cannot take into account the complex architectures of quantitative traits as are being revealed today.2. The nature of polygenes is discussed in detail from the theoretical point of view. In out breeding species, some form of the balanced polygenic complex is likely, showing polymorphism for the constituent genes. Although polymorphism is implicit in the argument, definitive evidence for poiymorphisms has only just appeared.3. There is no evidence that polygenes differ from any other gene.4. Several artificial selection experiments are described, in particular in Drosophila. By means of appropriate breeding techniques after obtaining responses to selection, genetic activity controlling quantitative traits can be located to chromosomes, and even specific loci found. Such few studies as have been carried out reveal, in general, the types of genetic architecture predicted on theoretical grounds.5. Selection for behavioural traits is considered briefly and it appears that no new principles are needed, except that careful environmental control and objective measurement present problems.6. The results of selection for quantitative traits in micro‐organisms reveal similarities to results in higher organisms in the few cases where definitive work has been carried out.7. Work on the simulation of models by computers has not greatly advanced selection experiment theory, mainly because, with few exceptions, linkage has been ignored.8. The existing theory on which selection experiments are based is inadequate for several reasons. It cannot predict the rate of response to selection nor the ultimate limits to selection, the nature of correlated responses to selection, nor the nature of gene segregation underlying the observed variability.9. Strains set up from single inseminated founder females from the same population of Drosophila have been shown to differ genetically for several quantitative traits. Therefore the base population is polymorphic for genes controlling these traits. This was exploited by carrying out directional selection on lines derived from those strains showing a high incidence of scutellar chaetae. This led to far more rapid responses to selection than lines derived from strains where the incidence of scutellar chaetae was lower.10. Ultimately, one can envisage the selection experiment as it is known today being partly replaced by the manipulation of located genes controlling quantitative traits into certain combinations.
ENVIRONMENTAL AND BIOLOGICAL CONTROLS ON BIVALVE SHELL MINERALOGY
Authors: KENNEDY WILLIAM JAMES , TAYLOR JOHN DAVID , HALL ANTHONY 
Published: January 2008

SummaryBivalves lay down two forms of calcium carbonate in their shells, aragonite and calcite. Shells may be wholly aragonitic, or may contain both aragonite and calcite, in separate monomineralic layers. Shells are built up of several layers of distinct aggregations of calcium carbonate crystals. These aggregations are referred to as shell structures and their general features are described. Aragonite occurs as prismatic, nacreous, crossed‐lamellar, complex crossed‐lamellar and homogeneous structures. Calcite occurs as prismatic or foliated structures. Myostracal layers (calcium carbonate laid down below sites of muscle attachment) are always aragonitic. The ligament and byssus when calcined are also invariably aragonitic. A summary of the occurrence of calcite and aragonite and the associated shell structures is given. Calcite is found only in the outer layer of superfamilies belonging to the subclass Pterio‐morphia with the exception of two species only from the Heterodont superfamily Chamacea. Generally within a superfamily shell structure and mineralogy are very constant. In all superfamilies these combinations have existed for many millions of years.It is therefore demonstrated that the prime control on shell mineralogy is genetic. Possible controls on mineralogy by the mantle cells, nature of the extrapallial fluid, nature of the periostracum and the organic matrix of the shell layers are discussed.It is known that environmental factors may modify the basic mineralogy/shell structure pattern within a superfamily. Thus there is an inverse relationship between the percentage of calcite in the shell and the mean temperature of the environment inhabited by the bivalve.A critical examination of published data shows that the evidence is convincing only in the superfamily Mytilacea. The species Mytilus californianus, which shows the greatest temperature effects, is peculiar amongst the Mytilacea in having an inner calcite layer as well as an outer one.Conflicting evidence for an inverse relationship between salinity and aragonite content is reviewed. The differences of opinion cannot be resolved without experimental work.We are grateful to the following for much useful discussion, and encouragement in many ways: Dr J. R. Baker, Dr G. E. Beedham, Dr B. C. M. Butler, Dr A. Hallam, Dr J. D. Hudson, Dr R. P. S. Jefferies, Mr J. Macrae, Dr W. S. McKerrow, Mr N. J. Morris, Mr C. P. Palmer, Mr N. Tebble, Dr E. R. Trueman and Professor A. Williams. Our best thanks are to Mr R. Cleevley for critically reviewing the manuscript.The following have rendered us considerable technical assistance: the staff of the electromicroscopy unit of the British Museum (Natural History), under the direction of Mr B. Martin; the technical staff of the Department of Geology, King's College, London and of the Department of Geology and Mineralogy, Oxford; Mrs J. M. Hall, and Mr G. Burton.