The present paper gives an account of the behaviour of the Golgi material, mitochondria, and nucleolar extrusions during the oogenesis of dog, cat, and rabbit. So far as the writer is aware there is no previous detailed work on the cytoplasmic components of the female germ-cells of the animals investigated.

R. Vander Stricht (1911) dealt with the oogenesis of the cat; O. Vander Stricht (1923) has made a comparative study of oogenesis of mammals, including the dog and the cat; P. del Rio Hortega (1913) described the behaviour of the Golgi material, and H. von Winiwarter (1900) studied the nuclear changes during oogenesis of the rabbit; H. von Winiwarter and G. Sainmont (1909) dealt with nuclear metamorphosis during the oogenesis of the cat; finally J. Nihoul (1926), in his paper on the rabbit, described the Golgi material during oogenesis. All the papers quoted, apart from those which deal with the nuclear changes, are either incomplete surveys, or the methods used are insufficiently delicate to reveal changes shown by modern techniques.

Comparative evidence on the topography, climate and chemical nature of the mammalian skin surface ecosystem is reviewed. Potential and established surface defence systems have been identified and their significance and interactions discussed in an attempt to provide a basis for further multidisciplinary study of the protective role of the skin surface, a function which is more extensive than hitherto recognised.

The hoatzin (Opisthocomus hoaziri) embryos are of special interest because the species is the only representative of its family and sub-order, and is well known to possess important anatomical features comparable with the bird-like reptiles. Eleven hoazin embryos collected by Dr G. S. Carter in British Guiana have been examined. These range in development from a stage having nine mesoderm segments—equivalent to a fowl embryo of approximately forty hours' incubation—to a single specimen ready to hatch. The earlier embryos resemble the corresponding stages in the development of other birds, but the oldest embryo shows features characteristic of the type and has been dissected. Points in the anatomy of this specimen and their bearing on previous observations on hoatzin embryos are discussed.

Man has found a diversity of uses for birch at least since Mesolithic times. In the mediaeval period, it was used for all kinds of domestic and agricultural purposes and it is remarkable how early its beneficial effects in silviculture were appreciated. Similarly, its amenity value has been appreciated for centuries in the rural scene and today it is employed in urban improvement too. Its importance for fuel and charcoal goes back into the distant past. Its bark is unique, with a range of end products from trinket boxes in northern Europe to large canoes in Canada. The trade in birch products is very large in eastern North America, while in Finland the plywood industry is also important. Birch will continue to play a significant role in British Forestry, both as a nurse species and as the main amenity species for poor and exposed sites.

The lives of the plants, animals and bacteria of the plankton are ruled by the diffusive nature of their fluid medium, in which vertical turbulence is sometimes checked by density gradients caused by surface heating or inflow of freshwater. Seasonal and spatial changes in the production and species composition of phytoplankton and associated microheterotrophs result from interactions amongst light penetration, supply of mineral nutrients, and vertical mixing; many species are capable of rapid increase when multiplication exceeds losses by dispersion and predation. Water depth, currents, dispersion and food supplies control mesozooplankton.

Although Scottish coastal waters include a variety of pelagic environments, there is little evidence of site-specific flora or fauna. Planktonic assemblages are, however, locally more diverse than expected. If this excess diversity is a result of ever-changing conditions, the composition of microplanktonic associations may be largely decided by chance. Explanations based on niche theory seem to apply convincingly only to the larger, semi-nektonic, pelagic crustaceans. Thus, consideration of issues relating to conservation raises fundamental and difficult questions about the biology of plankton.

Conservation of species is impractical if accident plays a large part in recruitment and replacement. Conversely, the dispersive nature of the pelagic environment and the weakness of interspecific relations may lessen the sensitivity of plankton to anthropogenic perturbations. Nevertheless, eutrophication and climatic change can disturb pelagic communities, especially in enclosed waters.

The hepatic flora of SW Asia strongly resembles that of the Mediterranean area; one notes only some Asiatic elements in the E and tropical African ones in the S. The only phytogeographical unit sufficiently well delimited at the level of hepatics corresponds to the Mesogean area, probably colonised, after the drying up of the Tethys, by species adapted to a dry climate and probably coming as much from the N as the S. This hepatic flora, unlike that of the phanerogams, is thus not diversified.

Although chilling of Arabidopsis thaliana cells to 4°C reduced respiration and superoxide generation, the latter still appears significant. Superoxide may contribute to the observed chilling-induced cellular lipid peroxidation and through processes that may be facilitated by the up-regulation of Cu,Zn-superoxide dismutase activity.

In the five years to 1978 hydrographic surveys were conducted in Sullom Voe, Shetland and these have been supplemented since 1976 by current measurements. Conditions varied from year to year mainly due to climatic factors, the most marked changes occurring at the head of the voe where varying degrees of stagnation were encountered.

In summer the voe is weakly stratified. In winter longitudinal gradients are encountered mainly because of a slight reduction in salinity towards the head. Because of this the surface waters of the voe are more readily flushed in summer than in winter when the flushing time, calculated from the freshwater balance, is at least 15 days. The current measurements show that rapid renewal of the surface waters occurs in the summer during storms. Because the voe is open to the north, southerly winds, blowing surface waters out of the voe, drive a much stronger circulation than winds from the north and this is the main reason for the intermittent breakdown of stagnation in the upper basin. Tidal currents are very weak (<7 cm/s) but occasionally seiches, generated by sudden changes in the wind direction, with a period of about 1 hour and current amplitude of 15 cm/s are encountered. Nutrients from the adjacent tidally mixed Yell Sound are intermittently supplied to the voe by these wind-driven processes and as a result, high levels of productivity are encountered at intervals throughout the summer.

Polystichum muricatum hybridises with both P. polyphyllum and P. speciosissimum on the Cerro de la Muerte in Costa Rica. Both hybrids are intermediate between their two parents in most of the assessed characters. True indusia, which are fully developed in P. muricatum, vestigial in P. polyphyllum, and absent in P. speciosissimum, are intermediate in mean development in both hybrids. However, one sorus is likely to have either a fully-developed indusium or a vestigial indusium. False indusia are characteristic of P. speciosissimum, but are vestigial to absent in its hybrid with P. muricatum. False-indusium development appears to behave as a recessive trait in the interaction of P. speciosissimum with P. muricatum.

Environmental disturbance has played a major role in the development of hybrids in Costa Rica. Mixed populations of the parent species are more common in disturbed terrain than in pristine areas, and hybrids are found only in disturbed terrain; this suggesting that disturbance promotes hybridisation.

The medusa Cosmetira pilosella Forbes is known, from the work of Miss M. J. Delap, to arise from a Cuspidella hydroid (Russell, 1936). Recently I found a small fertile colony of a Cuspidella on a dead bivalve shell dredged off Brigurd Buoy in the Firth of Clyde and this later liberated young medusæ in the laboratory. These were identified as Cosmetira pilosella, thus confirming that the hydroid of C. pilosella is a Cuspidella. There is no previous description of the hydroid or of the newly liberated medusa and so a description is given below.

The authenticity of birch collections is always in doubt unless one has wild source material; even the collections of Forrest, Wilson, Rock et at. may be suspect in that labels and records have been lost or confused. Collections are best maintained from vegetative sources and clonal selection is discussed. Site tolerances, planting problems and after-care are given detailed coverage. Species, hybrids and cultivars in general cultivation are listed and a summary of representation in British arboreta is included.

In the red deer population of the Isle of Rhum, the effects of increasing population density on reproduction and survival vary with the individual's sex, age. reproductive status, home-range quality, group size and social rank. Males are generally more strongly influenced than females. Within both sexes, individuals that are at an initial competitive disadvantage are generally most strongly influenced by rising density.

These differences are likeh to have far-reaching consequences. In particular, they may help to explain why dense deer populations commonly have female biased adult sex ratios: why calculations of maximum sustainable yield commonh overestimate the number of animals that can be culled; and why some populations that are not subiect to animal or human predation stabilize while others oscillate.

The distribution of thiol (sulphydryl) groups in the wool follicle has been studied with Bennett's reagent; the strongest reaction was found immediately proximal to the prekeratinization (keratogenous) region. Mice and lambs were injected with cystine labelled with sulphur-35 and radioactivity was detected in the follicles, autoradiographically within a few minutes. A peak of activity formed in the follicle during the first few hours after injection which suggested that there is a rapid turnover of cystine in the body. But a small amount of activity could still be detected in the follicle up to at least 3 weeks afterwards.

Sulphur seems to enter the follicle immediately above the bulb, and reaches the fibre first on the side at which it is keratinized last. This method indicated the relative proportion of sulphur in different regions of the follicle and suggested that the sulphur becomes concentrated on keratinization. No difference in sulphur content was found between primary and secondary follicles, the ortho- and paracortex, and apparently between cortex and medulla. When labelled sulphate was injected, activity appeared first in the outer sheath, and only later in the fibre.

The fossil plant described is a mould formed in a Clayband Ironstone nodule by the leaf cushions of a palæozoic arborescent Lycopod. It exhibits the unaltered three-dimensional shape of the surface of the tree-trunk. The description adds to the known facts about the leaf cushions and their diagnostic features. The specimen has been placed in a new species of the genus Sublepidophloios, Sublepidophloios ventricosus.

A new method of making casts from such fossil moulds is described which involves the use of an elastic, re-meltable plastic compound. An examination of casts made by this method indicates that the plant fragment described was fossilized with the minimum amount of compression and distortion.

Details of what occurs in the interval between the hatching of amœbulæ from the spores of the Proteus group of amœbæ to the attainment of the adult condition (4–6 months) not hitherto known are described. The method consists in removing mature adults to petri dishes 4 in. in diameter, containing a dilute inorganic fluid which causes sporulation. The subsequent development of the hatching amœbulaæ can be traced in situ by means of a 4·4 mm. water immersion lens, and is seen to consist of feeding and growth alternating with periods of encystment. The time spent in cysts greatly exceeds that of activity.

Some account of what takes place when cultures of the Proteus group, allowed to dry to a brownish dust, and then wetted, is given. Only in the case of A. proteus have the amœbulæ, which hatch out from the spores, been grown to maturity. It has been shown that the dried cultures used may comprise (1) spores, (2) cysts of varying size from which arise amœbulæ likewise varying in size.

At ten stations in the upper Tay Estuary, surface water, bottom water and sediment samples were taken on 25 March 1976, 5/6 May 1977, 11 April 1978 and 6 June 1978, and investigated quantitatively for the presence of lower marine fungi, chytrids and higher mycelial fungi by means of the water-culture baiting method with pine pollen. The distribution of fungi is discussed as a function of the physical characteristics of the estuary.

Two thermodynamic schemes have been developed to describe the CO2 system in sea water. The ‘pure’ treatment is based on the theory of dilute solutions and is general. The ‘pseudo’ treatment uses ‘stoichiometric’ constants related to the acidity constants of Bronsted (1928). It is empirical and specific to the medium in which the measurements are made. The pure thermodynamic treatment developed from the early attempts to characterise the various equilibria involving CO2, carbonic acid and its anions and was much influenced by the work of biochemists and physiologists on the blood plasma system. These attempts were initiated before the concepts of complete dissociation or of activities were developed. The subsequent application of these concepts was immediate and fruitful. By 1927, especially as a result of the work of Warburg and of Hastings and Sendroy, a consistent scheme had been developed for the NaCl—NaHCO3—Na2CO3 system. This work had also been extended to phosphate, citrate and blood plasma solutions and the discrepancies between the apparent activity coefficients discussed and tentatively ascribed to complex formation.

Johnston and co-workers developed the thermodynamic treatment of the carbonate system in natural waters and by 1920 understood the relation between ΣCO2, alkalinity and carbonate solubility and had identified and solved the major analytical difficulties.

The discovery of the interference due to complexing prompted various workers to determine empirical 'apparent' or stoichiometric constants. These are derived from the experimental data by assuming that a function analogous to the pure constant, but defined in terms of total species concentrations rather than activities, will behave like the pure constant over the temperature, salinity and pressure range of interest and will not vary with the concentration of any of the species it describes. Starting with the work of Moberg and Buch in the early 1930s, a complete scheme has been developed based on this treatment. The apparent constants for carbonic and boric acids in sea water are now known with sufficient accuracy to allow detailed study of the effect of water chemistry on the formation and dissolution of carbonates under any oceanic conditions.

I thank you most heartily for your gracious gesture in asking me to address you on this happy occasion. In one way or another, much of the work I shall report to you today was gathered or had its inception here in Edinburgh on earlier visits and I am, therefore, both grateful and proud to be given this opportunity to participate in this manner in the Challenger Expedition Centenary.

Loch Lomond is divisible into two natural regions, a northern, deep, steep-sided trough and a southern, relatively shallow expanse. These are separated by what is, in many respects, a transitional middle region. This topographical diversity has engendered widely different environments for the benthic fauna, especially for the profundal fauna.

A survey of selected sites in each region has shown a distribution of species in accordance with the individuality of these major divisions of the lake.

Chironomid midge larvae and the bivalve mollusc, Pisidium, each have dominant species in different regions. Of the former, Sergentia coracinus characterizes the northern and species of Tanytarsus the southern region; both being absent from the transitional region where Chironomidæ of any species are few in number.

Pisidium conventus predominates in the deep cold waters of the northern and middle regions and is replaced by other species, chiefly P. lilljeborgi, in the southern.

Regional differentiation of oligochaete worms appears to be less clearly defined but with Limnodrilus sp. avoiding the deep water and Stylodrilus heringianus favouring it.

Despite marked differences in proportions of the component species, tentative estimates of biomass of the profundal benthic animals show a tendency towards equality in all regions.

Fifty species of polychæte worms are listed which have not hitherto been recorded from the Clyde Sea area, and an account is given of the morphological differences which some of them show from the available descriptions. Of the fifty new records, nine are new to British waters, including one described as a new species, Amage scotica (Ampharetidæ).