The unsettled cool-maritime climate of the Outer Hebrides represents an extreme modification of that of the British Isles generally; yet while it imposes strains, as an environment for man it has long been far from unproductive. Frequency of rain as showers, wind, high humidity and slow evaporation provide difficulties; but there is a relatively long, if slow, growing season ending in a mild autumn. Results of instrumental observations over 120 years are discussed; trends are compared, but closer analysis is hampered by changes in location of station. Some indication of extent of gain from increased shelter is given.

Because of the wide latitudinal range of Sitka spruce, trees of different origin show very large differences in growth rate and adaptability when grown on a variety of sites in Britain. The Forestry Commission has forty-eight seed origin trials, planted between 1929 and 1975, which are now beginning to provide a good overall picture of this variation. On the other hand, differences in morphology and colour are relatively minor, so that it is very difficult to identify the seed origin of a stand of trees on visual grounds alone. Southerly origins (below Latitude 47°N) grow fastest, but they suffer more severe frost damage, particularly in the nursery, and tend to have lower density timber than those from 53°N or above.

During the winter of 1937–38 it became necessary to obtain the maximum number of offspring from a certain pen mating for the purposes of an experiment unconnected with the present report. Accordingly all suitable eggs were incubated, and since chicks were required all the year round the data which accumulated related to periods extending beyond the normal hatching season. Not long after the beginning of the project strikingly consistent differences between the records of the individual females became apparent, and interest in this phenomenon led to the decision to incubate every intact egg from the pen, irrespective of any normally undesirable characteristics of shell texture or shape. This was done for two years (1938–39), and provided the main data for the study of fertility and embryonic mortality reported here.

A review of current knowledge of the distribution of Palaeozoic ferns and fern-like plants is presented. Whilst numerous putative ferns occur in the Devonian, it is not until the Lower Carboniferous that ferns belonging to the Filicales appear. The Namurian represents a major gap in our knowledge. The ecology of late Palaeozoic ferns is reviewed. The association of early fern assemblages with volcanic terrains is considered particularly significant in the relationship between evolution and environment. Extinction of more specialised groups may have been caused by climatic changes.

Numerous theories exist to explain the mechanism of transport of organic carbon from its site of photosynthetic fixation to the point of its utilisation in the deep ocean. With one exception none has been adequately quantified. A new mechanism is proposed which suggests that the so-called olivegreen cells may contribute up to 35 per cent, of the carbon requirements of the benthic fauna. These conclusions are based on observations of their vertical distribution, the apparent labile nature of these cells and evidence of their presence in the guts of benthic and pelagic fauna.

The toxicity of bracken fern (Pteridium aquilinum (L) Kuhn) is complicated because this plant elaborates more than one type of agent potentially harmful to livestock.

When simple-stomached animals are fed a diet containing some green fronds or rhizomes for a few weeks, they develop anorexia and inco-ordination symptoms; this polyneuritic syndrome shows all the characteristics of thiamine deficiency. Thiamine therapy is effective in curing the animal provided it is administered at the onset of clinical symptoms.

Bracken staggers in the horse and rhizome poisoning of pigs are diseases of this nature,i.e. an avitaminosis B1 has been induced. The causative agent in the fern is a steam-labile enzyme, thiaminase I, which destroys thiamine in such a way that it is no longer active in animal nutrition.

Acute cattle bracken poisoning occurs after frequent eating of the fern over a period of weeks.Haemorrhages and fever are the characteristic clinical symptoms, and the animal usually dies within a few days. The fundamental lesion is bone marrow aplasia resulting in a severe leucopenia and thrombocytopenia.Thiaminase I is not involved in this disease. Bracken contains an organic chemical(s) which poisons rapidly dividing cells in the bovine animal. Sheep are less sensitive to this toxic agent, although the condition has been described along with 'bright-blindness* in some parts of Britain (e.g. North York Moors).

Purification of the active principle causing cattle bracken poisoning from green fronds and rhizomes is far advanced; these methods are described, along with calf toxicity tests on each fraction. Chemical investigations are also under way to determine the nature of the components.

Whether the cattle factor, in small doses over an extended period of time (years), is also the agent causing tumours in livestock, is probable but not certain. Some bracken constituents shown to be carcinogenic in small animals, e.g. shikimic acid, quercetin or the tannin fraction, are not capable of producing acute cattle bracken poisoning; neither does safrole or 1-indanone.

Some of the sesquiterpene glycosides—the 'pterosides' and/or their aglycones, the 'pterosins', of which over 30 have been identified in bracken—are likely candidates. On the other hand, the active principle(s) may be something quite different; the search continues.

Plants are killed by prolonged ice encasement at slightly subzero temperatures and under these anoxic conditions a number of metabolites are accumulated. Timothy grass plants encased in ice at −2°C can survive these conditions for many weeks and accumulate mainly CO2 and ethanol and lower levels of malate, oxalate, citrate, fumarate and pyruvate. While the accumulation of most of the metabolites increases towards the end of the encasement period the amount of malate decreases, indicating utilisation. Late in the encasement period lactate, butyrate, and traces of malonate, formate and tartarate were detected which might be of bacterial origin. The bacteria most commonly isolated from ice-encased plants is Pseudomonas fluorescens (Trevisan) which in most cases is saprophytic. All of the above-mentioned metabolites were also detected from thaw water in the field after long duration of ice encasement, butyrate attaining the highest concentration.

Viral erythrocytic necrosis (VEN) in fish is prevalent in a wide variety offish species. It has been detected in both wild and captive fish populations. The infection prevalence in wild populations of some fish species is correlated inversely with the age of the fish. VEN is characterised by cytoplasmic inclusions in circulating erythrocytes of infected fish; nuclear necrosis of erythrocytes may also be evident by light microscopy. The stage and degree of infection affect the type of cytology seen in VEN infections of different fish species. By electron microscopy, infected erythrocytes show spherical virions within the cytoplasm and the virion size is characteristic of the host erythrocytes infected. To date, knowledge of VEN viruses in fish is restricted to virus morphology and propagation in vivo, although preliminary studies have indicated the type of blood parameters which VEN can affect. No such virus has been fully isolated and characterised and all of Koch's postulates have not been fulfilled.

Structural changes induced in male auxocytes after formaldehyde feeding were analysed cytologically. In comparison with the effects of X-rays (on mature sperm) there is: (1) a high proportion of mosaics; (2) an excess of repeats and deficiencies; (3) a shortage of translocations, and (4) fewer breaks in the heterochromatic regions.

The very high frequency of mosaics and the low ratio of inter- to intrachromosomal changes may be explained by the delayed opening of potential breaks which tend to open simultaneously in the same chromosome but at different times in different chromosomes. The high number of “isochromatid” breaks (repeats) points to some connection with the reduplication cycle.

The shortage of “eu-heterochromatic” changes in which “heterochromatic” breaks in salivary gland analysis are scored, can be similarly explained by a difference in the time of opening of potential breaks in the two types of chromatin.

Initial non random distribution of breaks as well as the conditions of rejoining in premeiotic cells may also play some role.

Studies have been made on the incorporation of [8H]-deoxythymidine into the DNA of the livers of Rana catesbeiana tadpoles. When metamorphosis was induced with tri-iodothyronine, the specific activity of the nuclear DNA rose 5 days after administration of the hormone. In contrast, the specific activity of the DNA from the mitochondrial fraction rose grave–2 days after hormone administration.

In order to determine whether the in vivo change was due to alterations in the pool sizes of the DNA precursors, in vitro studies on DNA polymerase were carried out. It was found that under conditions where the enzyme activity was not limited by availability of template or substrates, there was a rise in the DNA polymerase activity in crude cell extracts from the tadpole liver. Fractionation of the cell components showed that little of this increment in activity appeared to be located in the nucleus, but that a large percentage alteration in activity occurred in the mitochondrial and cell sap fractions.

A possible interpretation of these results is that an increase in the mitochondrial DNA polymerase is one of the early effects of thyroid hormone. This possibility is discussed in relation to the other known effects of thyroid hormones in tadpoles, with particular reference to nucleic acid metabolism and also to mitochondrial hyperplasia.

According to Ellerman (1941), the seventy-odd forms of palæarctic rodents that go under the name of “True Hamsters” (family Murinæ, subfamily Cricetinæ) fall into four genera with a total of 18 species: Cricetulus (11), Phodopus (3), Cricetus (1), and Mesocricetus (3), the last two genera being unified by some authors. So far only one species of this important group has been investigated from the point of view of chromosome properties: the Golden Hamster, Cricetus (Mesocricetus) auratus Waterhouse.

The minimum energy requirements of trout and perch populations in Loch Leven, Kinross, were calculated for the year 1970–71. Use was made of laboratory data relating to oxygen consumption and ammonium nitrogen (NH3–N) output. Estimates of the specific dynamic action (SDA) of food material were made at 5°, 10° and 15°C and used to predict periods of growth. It was found that optimum growth would take place at 10°C, as opposed to 15°C, and that negative somatic production in the overwintering trout population was due to the energy content of the food intake being less than the minimum energy requirements of metabolism.

The entomology of birch in Britain (and to a lesser extent in Fennoscandia) is reviewed in broad ecological terms. In particular, the size of the associated fauna, the kinds of geographical distribution patterns seen for birch insects in Britain, birch defoliators, and the conservation needs of insects associated with birch in Scotland are considered. A closing section briefly outlines additional literature on the ecology of birch insects.

This paper considers the background, philosophy and desirability of the use of used automobile tyres in the construction of floating breakwaters for wave attenuation problems in general and their application to fish farm protection in particular. The method of construction and the assessment of performance are discussed.

Model tests using one quarter scale tyres in a hydrodynamics laboratory towing tank are described. By computerised data collection and processing, the wave attenuation characteristics were deduced for twentyfive breakwater designs made up from the two most commonly used tyre groups or modules. Wave induced loads on the catenary mooring system were also analysed for extreme values. This data forms part of a systematic study of scrap tyre breakwater design parameters and some conclusions can be drawn.

The implications of these model results are scaled to apply to the environmental requirements of fish farms and the relevance of the local topography is discussed.

Although current models of the roles of VA mycorrhizas in succession describe the fungal effects on the plant, they ignore the immigration patterns of the fungi. It is suggested here that the vectors of spore immigration (animals and wind) determine the pattern of re-invasion with respect to the patches of vegetation establishing on a disturbed site. The environment dictates the dominant vector. If invasion is facilitated by animals (locomotion), such as at Mount St Helens, they inoculate patches of plants, not individuals, and the patches change faster than immigration rates. Thus, the island biogeography equilibrium model is not applicable to describe VA mycorrhizal fungal establishment. If invasion is by wind (mass flow), such as in a cold desert system, inoculum is rapidly distributed across a site and VA mycorrhizal fungal richness and density rapidly equilibrates with its resource, a single shrub. By applying these models, a priori prediction of establishment following catastrophic disturbance might be possible, as opposed to mere description.

The study of genetic effects on the phenotype of gametes may be called the genetics of gametes. As evidence of such genetic effects, marked inter-strain differences have been demonstrated in characteristics of rabbit spermatozoa examined in nigrosin-eosin preparations. Strain differences have been found in the size and shape of the spermatozoan head, and in a measure of spermatozoan viability—the incidence of stained heads. A first comparison of the spermatozoa of specific breeds is given. The size of the spermatozoan head is to some extent independent of the body weight.

The Reverend T. R. R. Stebbing (1835–1926), who monographed the Challenger Amphipoda, was brought up in a literary and historical tradition, but became a convert to Darwinism and a naturalist about 1860. Canon A. M. Norman was responsible for the Challenger Amphipoda being offered to Stebbing in 1882. Stebbing's monograph, in 1888, describes the collections and contains a lengthy and definitive annotated bibliography of the Order. It also contains the first indication that the Amphipoda have evolved by adaptive radiation governed by Darwinian selection. Stebbing's later work on amphipod taxonomy contains no evolutionary speculation, although his scientific essays were uniformly and sometimes acrimoniously pro-Darwinian.

Stebbing treated 63 species of presumed deep-sea benthic gammaridean amphipods. Only 44 of these are now believed to be benthic. The Challenger's gear was inadequate for collection of small abyssal animals, and pelagic species make up an increasingly larger fraction of successively deeper ‘benthic’ samples. Consequently most knowledge of deep-sea benthic Amphipoda comes from work in the last 20 years. A deep-sea transect between Massachusetts and Bermuda has at least 108 species, with a maximum of 85 benthic. Distribution is similar to that of a transect off Oregon. Most of the species are in the families Ampeliscidae, Eusiridae, Lysianassidae, Oedicerotidae, Pardaliscidae, Phoxocephalidae and Synopiidae. There is a marked change of species with depth, categorised in six faunal groupings. Endemism is high in the North American basin and there is little affinity to high latitude faunas. Size and biomass decrease with depth.

Diversity of deep-sea Amphipoda is high and comparable to that of Polychaeta and Bivalvia. Present explanations for the high diversity (number of species) are all inadequate in the absence of accurate knowledge of the rate of food supply, diversity of selectively important resources, and rate of food supply, and there is little knowledge of reasons for the high genetic variability in deep-sea animals.

Seldom, if ever, in the long histories of the Scottish Universities can there have chanced a centenary such as we now commemorate. In the same year, 1854, there died in Edinburgh two celebrated occupants of the Regius Chair of Natural History in the University, one full of years, with solid achievement and half a century of academic service behind him, the other in the first year of his Professorship, in the full tide of life, whose great accomplishment held promise of greater still; the one the master, the other his brilliant pupil and successor—Robert Jameson and Edward Forbes. Each of these men, in his own way, added enormously to the factual stock of knowledge, but the greater contribution was that each, by precept and example, helped to modify and mould the outlook of naturalists throughout the civilized world.

In Meganyctiphanes the blood is pumped from the heart to the various regions of the body by way of a well-developed arterial system. It passes out of the open ends of the final sub-branches of the arteries into the various sinuses, finally collecting in the posterior ventral region of the thorax. From there, by the action of the pericardium and the muscles associated with the afferent branchial channels, it enters the afferent branchial channels whence it circulates through the branchial veins in the branchiæ, to the efferent branchial channels. The beating of the heart draws the blood into the pericardium whence it reaches the heart cavity by way of two pairs of ostia.