Administration, by dietary supplement, of ethylestrenol to rainbow trout and to salmon parr results in significant increases in growth rate; further treatment of smolts retained in fresh water reduces the growth rate. Treated parr develop into 1 + smolts in significantly lower proportion than controls, but have a higher condition factor.

Stress induces in rainbow trout long-lasting reductions in plasma thyroxine levels and increases in serum cortisol concentrations. The origin and significance of these changes is discussed.

The administration of 17β-oestradiol at 20 mg/kg of food for the first 30 days of feeding causes sex-reversal of male salmonids. Treatment with 17α-methyltestosterone at 3 mg/kg food for 90 days following first-feeding causes sex-reversal of female salmonids.

The flooding tolerance strategy of three tropical gallery forest species, Sebastiana klotzchyana, Hymenaea courbaril var. stilbocarpa and Chorisia speciosa was studied. Data from the flood-intolerant Schyzolobium parahyba have been included for comparison.

In the case of S. klotzchyana flooding induced an acceleration of glycolysis, with ethanol as the sole end product of anaerobic metabolism. Oxygen diffusion to the root system was not detectable.

The results obtained for H. courbaril and C. speciosa show a compromise between metabolic and morpho-anatomical adaptations to enable them to occupy seasonally flooded areas. In both species, at the onset of the stress, the roots stop producing high amounts of ethanol and lactate. diverting part of the pyruvate produced to malate. The amount of pyruvate converted into malate is determined by the amount of oxygen diffused from the aerial part to the roots. This is used to oxidise pyruvate through Krebs' cycle and the excess is converted to malate. ATP production in the root system is predominantly aerobic and therefore not linked to malate production.

The low level of acceleration of the fermentative pathway, coupled with the lack of oxygen diffusion to the root system, resulted in a significant decrease in the growth rate of S. parahyba.

The problem to be presented here emerges from the following groups of facts and more or less generally accepted opinions.

As heterochromatin we may define those parts of chromosomes which reach maximum nucleic acid charge in mitosis or meiosis in times other than metaphase. In salivary gland chromosomes (which are more conveniently called polytene chromosomes) of Drosophila melanogaster the proximal heterochromatic parts of all chromosomes come together and form a central undifferentiated mass, the chromocentre. Genetically heterochromatin forms the so-called inert regions of the chromosomes.

Floral ontogenesis has long been a preoccupation of morphologists. In trying to understand the physiological mechanism that underlies and determines the orderly formation of the several kinds of floral organs, it is essential to consider the organization and functional activities of the apex of the antecedent leafy shoot. The most general characteristic of the growing shoot apical meristem is that it gives rise to a succession of regularly spaced leaf primordia, sometimes of very variable form and structure, these having their inception in loci of special metabolism, or growth centres. The latter, typically originate in the sub-distal region of the meristem. The initial state of this region, which consists of equivalent embryonic cells, may be such that the reacting metabolic substances are homogeneously distributed in it. A contemporary chemical theory of morphogenesis envisages the possibility that a reaction system of this kind, in obedience to the laws of physical chemistry and mathematics, and on being activated, can give rise to a patternized distribution of metabolites, e.g. of growth centres, this constituting the chemical basis for the ensuing morphogenetic developments. This general property of the apex is maintained throughout the flora development, however much it may be modified in other ways. It is also known that the positions of new primordia are affected by those already present round the meristem.

A twig chamber system was developed for the exposure of mature trees to ozone (O3) under field conditions. The fumigation system allowed the exact control of O3 concentrations in the chambers, the measurement of O3 uptake as well as gas exchange measurements under ambient and controlled conditions during and after O3 fumigation. Because of differences in individual twigs the system should provide the exposure of replicates to different O3 treatments. Tests showed that temperature, humidity and O3 concentrations inside the chambers were comparable with diurnal courses observed in the field. Comparative gas exchange measurements indicated that there were no differences in net photosynthesis and conductance of twigs outside the chambers and twigs which remained within the chambers for 23 weeks receiving ambient air.

More than 300 bottom samples taken in the Rockall Trough and neighbouring areas (Northeast Atlantic) since 1973 provide an opportunity to study the distributions of the commoner megafaunal species. These include 131 species of echinoderms, for the most abundant of which the bathymetric and regional distributions are defined. Analysis of samples by means of the coincidence-of-range method along a bathymetric transect shows peaks-in the first and last occurrences of species at the 800–1200m and 1800 m levels. Cumulative curves of the recruitment of all echinoderm species with increasing depth show step-like increases in the rate of species recruitment with depth. These maxima in rate of faunal change are related to water–mass structure, particularly the depth of the seasonal and permanent thermoclines. A considerably broader bathymetric range is shown by post-larvae and juvenile stages compared to adults.

The deposition of reactive gases on terrestrial surfaces is one of the primary mechanisms by which pollutant gases are removed from the atmosphere. The chemical properties of the gases (SO2, NO2, HNO3, HCl) and of the absorbing surfaces lead to differing rates of exchange and controlling processes. The most reactive gases, HNO3, HCl (and for many surfaces NH3) exhibit negligible surface resistances; deposition velocities (Vg) appropriate for short vegetation ranging from 2 to 5 cm s−1, for forests Vg may approach 10 cm s−1. The large rates of deposition for NH3 on moorland and forests lead to annual inputs, in areas with large atmospheric concentrations of NH3 (≥ 5 μg NH3 m−3), ranging from 20 to 60 kg N ha−1. The net exchange of NH3 over cropland, attributable to deposition during vegetative growth and emission of NH3 during senescence, is less well known but believed to be small.

The co-deposition of NH3 and SO2 on external surfaces of plant canopies is believed to enhance SO2deposition with reported deposition velocities over short vegetation of 2.0 cm s−1.

Rates of cloud droplet deposition to vegetation have been shown to be very similar to rates of momentum deposition (i.e. Vt ≈ ram−1). These findings provide the basis for estimates of cloud deposition inputs of major ions to upland Britain where they may contribute up to 30% of the wet deposited sulphur and nitrogen.

The chromosome constitution of the bisexual beetle Ptinus clavipes Panzer (2n = 18) and of its gynogenetic form P. clavipes f. mobilis Moore (3n = 27) have been investigated. The triploid mobilis lives in close association with the bisexual species and mates freely with the males. Eggs from virgin females never pass beyond the metaphase stage and successful completion of maturation is dependent on the presence of sperm. An endomitotic split is apparent in prophase chromosomes and leads to the formation of twenty-seven pseudobivalents which undergo a pseudomeiotic division. Only one maturation division has been observed. Although the fate of the activating sperm has not been resolved it is thought that sperm nuclei give rise to isolated haploid nuclei in some eggs and interfere with normal cleavage in others. Since the triploid form may also mate with males of Ptinus pusillus Sturm and P. fur. L. with reduced numbers of progeny the affinities of the gynogenetic form is discussed. This is the only known case of gynogenesis in Coleoptera.

The historical review of scientific work done in the Outer Hebrides precedes a scientific profile of the archipelago including geographical, geological, botanical, zoological and resource outlines. Effects of the use of natural resources by man on the natural environment are discussed. Management of land and water for the purposes of nature conservation are given by descriptions of the Loch Druidibeg and Monach Islands National Nature Reserves and other Sites of Special Scientific Interest. These exemplify existing case studies and procedures in nature conservation conducted by the Nature Conservancy Council and others. In conclusion, the Outer Hebrides are set in the context of the National Planning Guidelines of the Scottish Development Department which show resources of ‘national’ importance in agriculture and nature conservation.

This paper gives results of a survey of the parasites of trout, perch, pike, stickleback and minnow carried out at Loch Leven between April 1967 and March 1972. Twenty-three species of parasites (Protozoa, Cestoda, Trematoda, Nematoda, Acanthocephala and Mollusca) were recorded from trout, 12 from perch, 11 from pike, 12 from sticklebacks and three from minnows. Details of the incidence and intensity of infestation of trout and perch by the parasites, except the Protozoa, are given. The parasites of trout are divided into loch and stream types.

The discovery (Auerbach, 1943, 1946; Auerbach and Robson, 1946, 1947) that mustard gas is comparable to X-rays and similar physical agencies in its ability to produce mutations and chromosome rearrangements has opened up a new line of approach to the problem of gene mutation. It is to be expected that a comparative study of the mechanism by which chemical substances on the one hand and physical agencies on the other exercise their mutagenic effects, will further our understanding of the process of mutation itself. One of the first questions to be tackled in the early days of radiation genetics was the possibility of a delayed mutagenic action of irradiation (Muller, 1927; Timoféeff-Ressovsky, 1930, 1931; Grüneberg, 1931). The bulk of the evidence (see, however, Bishop, 1942) indicates that X-ray-induced mutations and chromosome breaks arise as an immediate effect of the irradiation, although after treatment of mature spermatozoa new recombinations of broken chromosomes may be delayed until the spermatozoon has entered the egg. Data obtained by Stadler (1939) suggest that after ultra-violet radiation of pollen grains the mutational process often is not completed before the treated chromosome has split into its two daughter chromatids. This results in a high proportion of mosaics. A similarly high proportion of mosaics has been found in the progeny of Drosophila ♂♂ which had been treated with mustard gas (Auerbach, 1946; Auerbach and Robson, 1946). This raises the question of a possible delayed action of the chemical mutagenic treatment.

Forest decline in Europe is centred around areas where air pollution is heaviest. Although statistical relations are still debatable at the stand level, they are a basis for the discussion of mechanisms by which air pollutants affect forest health. The aetiologies of different syndromes of decline are discussed. Exposure to large concentrations of gaseous pollutants appears to have short-term rather than long-lasting effects, whereas pathogens seem to be of only secondary importance. The deposition of sulphur and nitrogen (nitrate and ammonium) pollutants has significantly modified soil chemistry and plant nutrition. In acidic low-pH soils spruce roots, instead of utilising nitrate, preferentially take up ammonium which interferes with the uptake of other cations, notably magnesium. The nitrate remaining in soil solution, as a result of the preferential uptake of ammonium, is leached together with sulphate to groundwater, accelerating soil acidification and further decreasing the calcium and/or magnesium to aluminium ratios in soil solution. Soil solution chemistry affects root development, and thus water and nutrient uptake. Canopy uptake of nitrogen, especially of ammonium, which is additional to root uptake, may occur and appears to stimulate growth inciting a nitrogen to cation imbalance with the consequential production of decline symptoms.

The diversity of biological functions that are exerted by toxins from snake and scorpion venoms is associated with a limited number of structural frameworks. At present, one predominant basic fold has been observed among scorpion toxins whereas six folds have been found among snake toxins. Most toxin folds have the capacity to accept multiple insertions, deletions and mutations and to exert various recognition functions. We suggest that such folds may serve as guides to engineer new protein functions.

The species composition, and the number of species of mammals, in the Guinea–Congo rain forests varies with locality. The highest species richness (up to 130 species) is found in parts of the West Central and East Central rain forest regions, and the lowest richness occurs in the Western Region and on the periphery of the rain forest zone. Rodents and bats contribute the greatest number of species (about 25% each), with lesser numbers of primates, duikers, and small insectivores; the relative numbers within each order is similar in all localities regardless of the composition and total numbers of species. The geographical distribution of each species is due to the alternating periods of forest fragmentation and expansion in the past, and the species-specific response to these environmental changes. There are about equal numbers of arboreal (30%), terrestrial (35%) and aerial (27%) species, each species within these categories having very specific habitat requirements within the forest. Most rain forest mammals are either frugivores (36%) or insectivores (37%): monkeys are mainly arboreal frugivores and folivores, and most prosimians are arboreal insectivores; forest duikers are terrestrial frugivores, and terrestrial rodents are frugivores or omnivores. Leaves, in spite of their abundance, are rarely eaten because of their low nutritive value and the difficulties of digesting them and consequently folivores (9%) are uncommon. Insects form the principal food for insect-bats and shrews. Mammals exhibit well-defined food partitioning in relation to food selection and body size, and therefore competition for food is probably minimal except during the dry season. Reproduction is more or less continuous in rodents and artiodactyis (with peaks of births at selected seasons); in contrast, monkeys and bats have fairly precise periods when births occur, which vary according to the species. The timing of reproductive events is regulated by the rainfall regime, availabiiity of food, and phyiogenetic characteristics such as the length of gestation and body size. Mammals interact with other rainforest organisms, principally as primary and secondary consumers, pollinators, and dispersers of fruits and seeds. Most species of rain forest mammals are solitary, but a few live in monospecific groups or in polyspecific groups. Forest disturbance in recent years (especially forest clearance and hunting) has had very detrimental effects on the geographical distribution and numbers of individuals of all species of forest mammals.

The branchial apparatus of Lampetra fluviatilis has been studied to find out whether the inspiratory movement is brought about by muscular contraction. Differences between existing accounts of the anatomy are pointed out, and a description is given of diagonal muscles which span re-entrant curves of the gill bars. Extirpation and stimulation experiments provide evidence that none of the available muscle groups can have an inspiratory function. The pressure changes in the gill sac indicate that the momentum of the water-stream in forceful expiration leaves a region of low pressure which initiates the inspiratory flow.

The rapid spread of bracken in some parts of the country has led to considerable investigation into the habits of the plant. But in almost all cases it is the spread of the adult sporophyte which has been described, and little attention has been paid to the insignificant, complementary half of the life cycle—the prothallus. Nor does any attempt appear to have been made to assess the rate of development of the prothallus and the young sporeling. A recent attempt to collect records of the occurrence of prothalli and young sporophytes in the field has shown how seldom they are found, and has emphasised the fact that little is known of the extent to which the plant spreads by the initiation of new colonies from spores (White, 1930).

Though our knowledge of the circulation in this complex region is still incomplete, recent direct current measurements have identified four separate elements of the circulation which appear to undergo a seasonal variation of some sort. These are: (i) a summer-autumn maximum in the deep overflow of Norwegian Sea Deep Water across the Wyville-Thomson Ridge; (ii) an autumn minimum in the upper-ocean circulation around Rockall Bank, ascribed to Taylor Column processes; (iii) an autumn-winter maximum in the strength and breadth of the slope current along the European continental margin; (iv) a winter-spring maximum in eddy kinetic energy in the open waters of the Rockall Channel, and over the full depth range, as a function of windstress and stratification. The first three of these elements are of localised occurrence along the northern, western and eastern margins of the Channel and are described only briefly. The fourth process, encountered at a range of sites in the northeast Atlantic, is described in detail using a total data set of 68 instrument-years of direct current measurements recovered from the Rockall Channel in 1977–84. In the seasonally-varying 3–27 day (d) band of periods, eddy kinetic energies (kE) are shown to be depth-dependent in amplitude, but with little evidence of any significant phase-lag with either depth or location between the individual timeseries of kE estimates. These time-series demonstrate clearly and for the first time that the winterspring peaks in eddy kinetic energy lag the winter peaks in windstress by between 1 and 3 months. This phase-lag is explained as the cumulative result of wind forcing and eddy dissipation.

This paper is an account of the development of the International Fisheries Commissions. Excluded are the commissions under the aegis of FAO: an earlier group, for example the Indo-Pacific Fisheries Commission, are only advisory, and later ones, like the Atlantic Tuna Commission, have not been in existence for long enough to discern characteristics in their activity. The activities of the Russo-Japanese commissions in the north-west Pacific are also excluded, because their actions do not have great influence on the older commissions or upon the newer ones established in the last five years or so. Although the International Council for the Exploration of the Sea has now only an advisory function in the North-East Atlantic Fisheries Commission, during its earlier history before World War II it was always able to act through the Danish Foreign Office. But a much more important point is that the International Council played a historically dominant part in the early development of many of the commissions, except of course those which originated in the north-east Pacific.

The Inner Hebrides support a diverse flora and a wide range of vegetation types today. Native woodland is rare, even on the larger islands of Skye and Mull. The present-day floristic and vegetational diversity and the scarcity of native woodland raise important ecological questions, answers to which can be provided by pollen analysis of loch or bog sediments.

Pollen analysis of sediments deposited during the last glacial stage on Skye and on Lewis suggest that some plants may have survived the last glaciation within the Hebrides. Pollen analysis of late-glacial (13500–10000 years ago) sediments on Skye indicate that even at the close of the last glaciation there was considerable floristic and vegetational diversity related to geology, altitude, and climate.

Post-glacial (10000–0 year ago) vegetational histories are available from Skye, Soay, Canna, Tiree, and Jura. Forest was rare or absent on Canna and Tiree as well as on the Outer Hebrides throughout the postglacial. In contrast Soay and southern and eastern Skye were well forested, with birch, alder, hazel, and small amounts of elm and oak. Pine was confined to eastern Skye. Since 5,000 years ago there has been extensive forest destruction by man, especially on the better soils, and the spread of bog and heath on the poorer soils. Northern Skye supported birch, hazel, and willow scrub during the post-glacial. This has largely been removed by man since about 5,000 years ago. The present-day vegetation of the Inner Hebrides is predominantly anthropogenic.

The respective ecological amplitudes of the two British tree species of Betula are known only imperfectly. B. pendula is better represented on drier, lighter soils and is more of a southern, eastern and lowland species than B. pubescens, which belongs rather to the wetter, colder conditions of north, west and upland Britain. The contribution of the two species to different types of woodland community is briefly reviewed in this paper, and consideration is given to the status of ‘pure’ birchwoods. In some cases, the latter may have been derived from other woodland types; in others, by invasion of heath or grassland. However, some relict birchwoods above the altitudinal limits of dominance by other trees, and in the extreme north and west of Scotland, may be ‘natural’ or ‘climax’ woods.

Birches show a number of characteristics of ‘r-selected’ plants and hence tend to be trees of secondary or seral woodlands. Factors determining the capacity of birch species to colonize bare ground or vegetation such as heath and grassland, are reviewed, with special reference to a study of invasion of Calluna heath at Dinnet, Aberdeenshire. The importance of the development of gaps in the Calluna canopy, or alternatively of fire, in providing suitable sites for establishment, is emphasized.

Changes in the ground vegetation following the establishment of birch stands are outlined, as well as the subsequent development of seral birchwoods. Attention is drawn to the fact that many upland birchwoods are becoming moribund, and to the effects of grazing and other influences in preventing regeneration. The possibility of reversing this trend is discussed.