A typical poultry flock consists of offspring from a number of sires each mated to several dams. In choosing male parents in a selection programme no criterion of individual merit may be available and selection must usually be based on the performance of related females. The present report deals with the theoretical efficiencies of three systems of selection of males

(1) on the average performance of the dam family of a male's sisters.

(2) on the average performance of the sire family of a male's full- and half-sisters.

(3) on a weighted combination of sire family and dam family averages.

For traits of low heritability system (2) may offer marked advantages over system (1), the only type of family selection previously investigated. This should prove of importance in flocks where recording facilities are limited. Providing environmental effects can be minimised, efficient selection may be based on the average performance of sire families housed as units without individual recording.

The efficiency of system (2) declines with increasing heritability and is also subject to complications introduced by population size. In all cases, however, optimum gains may be obtained on system (3) when both dam family and sire family records are available.

An understanding of the movement of a body of water can be considered a prerequisite to any other study whether it be physical or biological. This is particularly so in the case of an estuary where the water movements are complex. The movement of water in an estuary is primarily governed by the tidal and freshwater inputs, the resulting flow being modified by bed and channel configurations, salinity, and siltload variations. The tidal and freshwater inputs are themselves variables, the tidal range varying with the lunar cycle, and the freshwater input varying with the season or rainfall. The salinity variations within an estuary are interlinked with the tidal and freshwater fluctuating inputs. In addition the local and regional weather can modify the tidal response.

Data on the evolution of nitrogen gas and methane, and the utilisation of nitrate were obtained from sediment-water interface core samples obtained from Loch Leven, Kinross, and Windermere Esthwaite Water, Coniston Water and Ennerdale Water in the English Lake District. Differences in the rate of evolution and total quantity of the gases are discussed in relation to the trophic state of the lakes. The potential importance of nitrogen gas loss to the nitrogen budget of the lakes is considered.

The age structure, both on the ramet and the genet level of boreal willow populations (Salix myrsinifolia-phylicifolia) was studied in relation to fluctuations in populations of voles (Clethrionomys glareolus and Microtus agrestis). Willow ramets were collected from four different areas in the coastal part of Sweden and Finland at the Bothnian Bay. In each area we selected one mainland and one island locality. The ramets, as well as the scars left by bark-eating voles on the ramets, were aged. We found in general a high correlation between ramet ages and peaks in vole cycles (based on frequencies of scars).

From a sample of 79 willow clones where all ramets were aged, more than half of the ramets were produced the summer following a vole peak. Field surveys of seedling survival showed that successful establishment is mainly confined to disturbed ground (vole run-ways, etc.) in connection with vole peak years. It is concluded that the age structure both at the genet and the ramet level in boreal willow populations are strongly influenced by the fluctuations in vole populations. The consequences of vole herbivory are manifold, e.g. periodic damage of willows may delay senescence of individual genets and delay the rate of succession due to increased opportunities for willow recruitment.

Land use and land tenure in the Uists has evolved over the past two centuries fashioned by the possibilities offered by the varying qualities of soils and terrain and by economic circumstances, estate and government policies. At the end of the 18th century, estate surveys and plans provide a detailed account of the patterns of tenure and land use. The crofting system, created between 1814 and 1818, with the aim of improving agricultural standards and as a means of maintaining a labour force to manufacture kelp, led to an expansion of the cultivated area. In the middle of the 19th century, large farms displaced much of the population and resulted in congestion in the remaining crofting townships and very intensive use of the available land. Government intervention led to the settlement of crofters on the majority of the farms after 1890. Since the ‘agricultural revolution’ of the 1950s, if the number of active crofters and croft units and the area of cropped land has declined, the size of the effective croft units and their cattle stocks has increased, particularly in the more recently formed townships. Cereal cropping is now virtually confined to the machairs and most of the crofts are under permanent grass.

The aquatic fern Azolla has a symbiotic relationship with an N2-fixing cyanobacterium. Fanners in China and Vietnam have used Azolla for centuries as a green manure for rice and as fodder for pigs, ducks and fish. Chinese researchers have been studying Azolla since the early 1950's but many of their achievements are unknown outside China because of language and other communication problems. This article reviews current Chinese Azolla research and focuses on the impact of newly introduced Azolla species in the areas of field application, use of spores, and isolation of the N2-fixing symbiont.

Like the world's oceans themselves, the Challenger Expedition overwhelms us by its vastness. In whatever direction one turns, the statistics speak of a copiousness, a completeness comparable to the other monuments to Victorian self-confidence. Challenger's cruise lasted 41 months; in 710 days at sea the ship travelled 69 000 miles around the globe on 4600 tons of coal. The ocean bottom was sounded 370 times, 255 serial temperatures were taken, and from the hauls of trawl and dredge at 240 stations came 600 cases of specimens animal, vegetable and mineral [2]. The 50 royal quarto volumes published over 16 years make the Report on the Scientific Results of the Voyage probably the major single research project of all time, with their nearly 30 000 pages of letterpress and more than 3000 lithographic plates, 200 maps and copious woodcuts. For more than two decades, from its announcement at the British Association meeting of 1871 to the banquet held to commemorate the publication of the final volume in 1895, the Challenger Expedition and its Report occupied the entire lives of some dozen men and substantial portions of the lives of many hundreds more.

The morphological variation between and within species of Betula has resulted in taxonomic confusion which chromosome studies have been aimed at reducing. The paper briefly reviews the general situation and summarizes recent work at Aberdeen.

Betula forms a polyploid series with chromosome numbers ranging from 2n = 28 to 2n = 84. The native British arborescent birches B. pendula and B. pubescens Ehrh. have respectively 2n = 28 and 2n = 56 chromosomes. Meiosis is essentially regular but many phenomena occur which may account for the production of gametes with non-haploid chromosome numbers. Variation in somatic chromosome number within the leaf tissues of both species is common and trees have been identified whose modal chromosome counts lie between 28 and 56. Some of these trees are of hybrid origin while others may aneuploid B. pubescens. The former types are sterile while the latter cross freely amongst themselves and with 2n = 28 and 2n=56 trees.

The growth and development of Sitka spruce roots is reviewed against the practical background of tree stability. Two features of the roots which make Sitka spruce liable to windthrow on upland sites are the shallow development in unfavourable soil conditions, and restricted lateral spread and anchorage caused by some forms of cultivation. Responses to different aspects of the soil environment are discussed, with emphasis on mineral nutrition, drying of the soil, waterlogging and temperature. The development of a small number of major woody roots from an assortment of primary laterals on the transplant occurs at an early age and is determined both by the relative size and vigour of the primary roots and by their local environment. The roots, which respond to increases in nitrogen and phosphorus supply with enhanced growth, are sensitive to drying of the soil and are particularly so to waterlogging, but they show no unusual response to soil temperature. Adventitious roots can play a role in the survival and development of the root system.

Phenolic secondary compounds and trichomes are instrumental in the regulation of herbivory on Salicaceae. The roles of phenolics in willows as toxins or deterrents, as phagostimulants or ovipository signals, and as precursors in insect chemical defence are briefly reviewed. The interactions between salicaceous plants, herbivores and their predators are discussed in the context of theories on the evolution of interactions among three trophic levels.

The status of insects on Sitka spruce in Britain is examined in relation to the attributes of this tree as a widely planted exotic. Both time in Britain and particularly the area planted influence insect species diversity. The abundance and status of selected insects of pest importance are examined. Future trends receive attention, particularly in relation to potential importation of pest insects and this is examined for a number of species from Europe and North America.

Bracken, Pleridium aquilinum, has long been present in Britain as part of the native flora. Before the arrival of man, Britain was a wooded and forested country, and in this vegetation bracken was an open woodland and forest margin species, which played only a relatively minor vegetational role. Its biology is such, however, that this plant is able to spread rapidly in response to removal of the forest canopy, developing into colonies which are much more ecologically aggressive and dominating than was the original habit of the plant when undisturbed.

In open conditions, bracken also has a far greater spore output than in more shaded ones. It is able to establish anew from spores only in relatively virgin soil conditions, particularly those produced by burning of other vegetation. Burning also benefits established bracken by removal of its competitors, whilst heavy and selective grazing by sheep also slowly reduces the natural vegetation competition in favour of bracken's further spread.

The history of the spread of bracken in Britain from palynological and historical evidence is reviewed in the light of this biology and, in particular, its spread as man has progressively removed the forest canopy,introduced steady heavy grazing pressure, and has burned, and continues to burn, vegetation.

The important macrophyte-feeding cyprinid fish Ctenopharyngodon idella Val., the White Amur or Grass Carp, is native to temperate climates. The present paper is concerned with its biology when transplanted to Malacca, a tropical research station in latitude 2° 17′ N.

At this station, the fish has a faster growth-rate, and may mature at an earlier age and smaller size, than in its native habitat. There are no marked seasonal changes at Malacca, and in these conditions the Grass Carp shows no spawning cycle, but some fish are ripe at any time of the year. While the testes of the males appear to develop normal milt, the ovaries in the fish examined seldom produced as many eggs as in their native habitat, and the eggs themselves have been shown to be mostly defective and to undergo early atresion.

Consequently, though the ovulation of eggs of normal size was induced by pituitary injection in nineteen out of forty-eight trials, no success was got in the artificial fertilization of the eggs, though elsewhere success has been got in 25 per cent and more of trials. It is suggested that this fish may need the external stimuli which are associated with its natural spawning season to develope normal fertile eggs.

The watermark disease is caused by the bacterium Erwinia salicis. It affects six species of tree willow and of these the white willow (Salix alba) and certain of its varieties are particularly susceptible. Unusually for a bacterial disease, the pathogen only colonises the xylem tissues, which become discoloured as a result. Watermark causes severe losses in S. alba var. caerulea, the cricket bat willow, and in several Dutch clones of S. alba which have been widely planted in that country. Although numerous studies have been made of its epidemiology since the disease was first reported in 1924, the infection process remains clusive. Recent research, much of it unpublished, points to the widespread occurrence of symptomless infection, and the possible role of this in the transmission of disease through the propagating material.

Material of a very small and distinctive species of Isoetes was sent by Miss Alison Baird in 1934 to Professor J. Walton, who kindly handed it over to me for examination. This species, hitherto undescribed, is here named Isoetes australis. The material, which consisted of plants of all ages from two-leaved sporelings up to adult plants, had been collected in 1930 from rock pools in granite outcrops at Bruce Rock, 150 miles inland from Perth, Western Australia.

The following description is mainly based on Miss Baird's material, but I later received air-dried plants of the same species which had been grown by Professor T. G. B. Osborn in the Laboratory at Sydney. These plants had originally been collected by E. T. Bailey from the Bruce Rock locality in 1934. They proved to be viable and commenced growth within a few days when placed in water, and I was able to keep one of them alive for a period of two years, though only in a depauperate condition. Professor Osborn also sent me herbarium specimens, collected in the same locality by Bailey, and some of these plants, which had been completely dry for six months or longer, proved viable, though I was unable to grow them on for more than a few months.

Ripening of tomato and other fruits involves changes in quality attributes that make them attractive to consumers. These alterations are brought about by the coordinated expression of specific genes. Ethylene, synthesised by cells of climacteric fruit at the onset of ripening, stimulates the expression of genes required for ripening to occur. Experiments with transgenic plants have shown that a 5′ flanking region from the fruit polygalacturonase (PG) gene directs the ripening-specific expression of foreign genes in tomato. Antisense genes have also been used to down-regulate expression of the PG gene, causing a reduction in pectin degradation during ripening. This reduction in PG has beneficial effects on fruit storage life and processing characteristics. Antisense technology has also been used to assign functions to previously unknown genes. This has led to the identification of the gene for ethylene forming enzyme (EFE) which catalyses the terminal step in ethylene synthesis. Detached fruit from tomato plants in which EFE is inhibited by antisense genes produce much less ethylene and ripening is greatly slowed. The rate of ripening can be restored by adding ethylene externally. These results raise the possibility of manipulating ripening of many fruits and also of controlling processes such as abscission and senescence of leaves and flowers.

In two earlier publications the author has suggested a theory of genetically determined asymmetries. Inherited asymmetry may be of two types. Many characters are unilateral (e.g. the aortic arch or the tricuspid valve of the human heart) or in some other way placed asymmetrically (e.g. the differentiation of organs along the cephalad-caudad axis of the body). The orientation of such gross asymmetries is in general irreversible. The author has pointed out that the study of uniovular twins which exhibit mirror-image similarities draws attention to a smaller class of reversible asymmetries. While an asymmetrical disposition of such a character is transmitted, its orientation is not fixed in the process of transmission. Thus a character may show itself on the left side in one generation or in one individual of a litter, and on the right side in another generation or in a litter mate. The extreme types of variation between which many transitional forms may be found are:

(a) From left to right, or vice versa.

(b) From caudad to cephalad extremity, or vice versa.

(c) From dorsal to ventral surface, or vice versa.

The natural distribution of Sitka spruce is examined in relation to the species' role in British forestry. Particular attention is therefore given to a description of habitats on the Queen Charlotte Islands, and also on the adjacent mainland of British Columbia where Sitka spruce is sympatric with white spruce (Picea glauca) and hybridisation occurs. Examples of genetic variation are given and it is suggested that a knowledge of the genecologv of the species in its natural habitat would help to elucidate its full ecological and genetic potential in Britain.

An account of the pathology of Sitka spruce in northern Britain is given based on enquiries dealt with by the Pathology Branch of the Forestry Commission Research Division in the last fifteen years. Sitka spruce occupies the major proportion of our forest estate but has given rise to only 15% of enquiries concerning tree damage. The most frequently diagnosed injuries have been those due to frost and to root diseases caused by Heterobasidion annosum and Armillaria spp. Two other root pathogens, Rhizina undulata and Phaeolus schweinitzii, and two needle pathogens, Lophodermiun piceae and Rhizosphaera kalkhoffii, have also been recorded in Sitka spruce plantations as have several wound-infecting stem decay fungi. Only five other fungal diseases, those caused by Botrytis cinerea, Phytophthora citricola, Helicobasidium purpureum, Sirococcus strobilinus and Pythium spp. have been recorded, all in nurseries.

The fishery for Norway lobsters Nephrops norvegicus began in the 1950s and has since become one of the most valuable assets of the Clyde Sea Area. Landings of Nephrops reached a peak of 26001 in 1972. Following a decline in landings up to 1975 there has been a further increase to over 45001 in 1983, valued at £4–5 million. Most of the landings are made by inshore trawlers working from Ayr, Troon, Girvan, Largs, Campbeltown and Tarbert. Recently a small creel fishery has developed in some sea lochs. The abundance of the stock appears to have been maintained; landings per unit of fishing effort have fluctuated without any obvious trend.

Since September, 1979. several aspects of the biology of Nephrops have been studied in an area south of the Little Cumbrae at the north end of the east Arran Basin. Data are presented on the density, size composition, growth rate, reproductive biology and feeding of Nephrops in this area. The results are compared with those obtained for other Nephrops populations, revealing some unusual features of Clyde Nephrops. In the Clyde, densities were lower than in a number of other areas, while growth rate was much higher and animals grew to larger sizes. Sexual maturity was attained at a larger size in Clyde Nephrops and studies of ovary development revealed that considerable numbers of large females did not reproduce annually, in contrast to some other areas. Recent observations suggest that the biological characteristics of Nephrops populations in an area may be influenced by features of the local physical environment such as the particle size distribution and organic carbon content of the sediment. Differences between Clyde Nephrops and those from other areas are discussed in relation to this.