An account was previously given of the discovery of two cases of placental fusion in mice, and it was suggested that this condition might occur fairly frequently. This has been amply borne out by subsequent experience, as fourteen other examples have been found while working with mice, and in addition it has once been found in the rat. From this additional material further information about the types of developmental abnormalities that may result from this condition has been gathered. Since the last paper, Owen (1945) has found that commingling of the fœtal circulations in cattle twins can result in the transfer of erythrocyte precursors between partners, resulting in animals exhibiting blood-groups bearing no relation to their genotype. Similar transfers in mice would lead to confusion in many genetic experiments, especially in transplantation experiments with tumours.

No genetical basis for the condition is apparent from the data available. It has been, noted in three matings of CBA mice, two of C3H mice, eight C3♂ × CBA♀, and three stock mice, the proportions being roughly related to the relative numbers of each type examined at the time of littering. The frequency is rather less than 1 per cent, of all placentas seen. The only common feature, to which attention was also drawn in the previous paper, has been that the fusion occurred always in conditions of uterine crowding due to large litter size. The smallest litter size in which this fusion was found was five, but in this case five placentas were present in one horn. Whenever labour was observed, it appeared to be difficult and prolonged. Once, by good fortune, delivery was timed approximately. A CBA mouse was found to have delivered two young, and two more were born within the next ten minutes. Nothing further appeared for two hours and ten minutes, when a live pair with fused placentas was delivered with some distress. The last two of the litter, making eight in all, were delivered within twenty minutes of the completion of the birth of the fused pair

The cutaneous reactions induced in the skin of human volunteers by protein A from Staphylococcus aureus have been studied. This cell wall protein induces no response when applied in solution to intact skin. In contrast a vigorous inflammatory reaction is seen if it is injected intradermally or applied to skin from which the stratum corneum has been partially removed. This study demonstrates that the intact epidermis is an important protection against this microbial product.

According to Borst (1913) each individual should be regarded as a specific biochemical system, and within this common background the different organs and tissues work together whilst preserving their own characteristics. On such a foundation, strengthened by the results of his own extensive experiments, Loeb (1930,1945) has built up his conception of the biological basis of individuality. According to his thesis the individuality of a tissue is a summation and integration of qualities in respect of its identity as a particular tissue or organ, in respect of the organism of which it is a part, and in respect of the species and order of this organism. The autograft is attuned to the biochemical system of the organism and is therefore accepted as a transplant, but the host reacts to the homograft (and more so to the heterograft) and makes an effort to destroy it. While the extent of the host reaction depends on many factors—e.g. genetical relationship, age of host and donor, etc.—the ability of different organs and tissues to survive as homografts varies considerably. It is, for example, well known that homografts of cartilage and cornea survive within the host long after homografts of other tissues and organs have been destroyed.

To regard the more prolonged survival of homografts of cartilage and cornea as evidence of low tissue specificity (Loeb, 1930, 1945) still leaves undetermined the real reason why these particular tissues are less readily overwhelmed by those of the host.

Knowledge concerning the meiofauna of the Forth is reviewed and extended by presentation of the results of new surveys of the intertidal and subtidal provinces of the estuary. Most of the published information concerns the influence of sewage pollution on shores of the firth. Before 1979, the meiofaunal communities of sandy beaches along the Edinburgh coastline exhibited reduced species richness, although certain taxa displayed enhanced densities. Improvements in the sewage treatment process have initiated a phase of meiofaunal recovery.

In the estuary the salinity regime plays a key role in the determination of species composition, although the influence of local changes in sediment type and stability is recognised. Meiofaunal communities of lower shore mudflats in different salinity zones of the estuary are described. Pollution plays a major modifying role. In the upper reaches of the estuary, which suffer oxygen depletion in summer, only nematodes and oligochaetes were recorded in the oligohaline zone and impoverished nematode and copepod faunas in the mesohaline zone. In the polyhaline zone discharges from the industrialised region around Grangemouth modify meiofaunal community structure over an extensive area of mudflat. The subtidal meiofauna of the lower estuary is briefly described, particularly with respect to the copepods. Impoverishment again occurs in the vicinity of Grangemouth.

Human skin propionibacteria have been shown to produce, in vitro, a wide range of inhibitory substances including bacteriocins, bacteriolytic enzymes, bacteriophages and low molecular weight metabolites (e.g. ammonia, propionic acid). Some or all of these substances may play a role in the ecology of cutaneous populations of micro-organisms and may be involved in maintaining the balance of the normal flora. There is no evidence to suggest that they deter or exclude other transient bacteria including pathogens. Similarly, evidence in support of the in vivo production of growth inhibitors by propionibacteria with activity against other skin micro-organisms is lacking (except for bacteriophage and propionic acid) so that their potential role in controlling cutaneous populations must be interpreted with caution.

The long history of discharge of industrial and domestic waste to the Forth makes the area of particular interest to environmental scientists. The area has been studied both in its own right for the monitoring and control of contamination by trace metals and organohalogen compounds, and in the study of processes which influence the dispersion and effects of these substances. This paper discusses the inputs of contaminants to the area, their occurrence in the water, sediments and biota, and places the Forth in context with other coastal areas of Scotland. The paucity of information concerning organohalogen compounds is contrasted with the extensive work carried out on trace metals.

It is no longer doubted that calcium functions as a second messenger in animals and plants. This is only possible because cells maintain cytosolic calcium concentrations many orders of magnitude below that of extracellular or organelle calcium. Environmental stimuli are perceived by receptor proteins which trigger transient elevation of cytosolic calcium using internal or external sources. The spatial and temporal distribution and the magnitude of calcium elevation determines the specific cellular response at the molecular level (Cheek 1991). The fine balance of cytosolic calcium homeostasis in animal cells is highly sensitive to oxidising conditions (Duncan 1991). Elevated cytosolic calcium resulting from oxidative perturbation of calcium homeostasis is believed to be responsible for the subsequent cellular injury and death (Nicotera et al. 1991). Transient stimulation of cytosolic calcium in sublethal oxidative stress may be a mechanism by which oxidative attack is perceived by the animal cell (Nicotera et al. 1991). Our understanding of oxidative stress and plant responses to it would be greatly advanced if it can be shown that similar processes occur in plant cells. This paper briefly presents the mechanism of oxidative disruption of calcium homeostasis in animal cells and summarises the evidence that the same scenario applies to plants.

Current research into viral monoclonal antibodies is reviewed in the light of their use or potential use as diagnostic reagents. Special attention is paid to influenza, the adenovirus group, herpes virus hominis types 1 and 2, rota viruses, hepatitis and cytomegalovirus. Although monoclonal antibodies have many advantages, particularly as regards specificity, purity, reproducibility, homogeneity and availability in unlimited supplies, certain problems are inherent in their very nature. Their preciseness may in fact be a hindrance to their use in diagnosis necessitating their recombination in pools and the quality assessment of their reactions with their homologous 'wild" types presents large logistic problems. There is no doubt that a powerful new serological tool has become available but their large-scale diagnostic use may be a little premature.

Regular moulting can prevent colonisation of the skin surface by epibionts, although some invading organisms are sufficiently mobile to overcome this protective device. Bacteria and sessile protozoans settle on the surface of the claws of Xenopus, where the keratinised cells are not shed as regularly as on the skin. Alternatively, parasites may inhabit the orifices, which also are not affected by moulting.

When one has spent—or mis-spent—substantial fractions of many years in gathering materials for a study and has eventually seen the results published in book form one is strongly conscious of a need to forget; at the very least there is a wish not to live in repetitious ways. An ancient Arab proverb, possibly relevant here, runs something like this: the word you have spoken is your master; the word you have not spoken is your slave. And so it is with my book The Gift Relationship which I sub-titled From Human Blood to Social Policy.

Parsley (Petroselinum crispum L.) is known to respond to pathogen attack by the synthesis of furanocoumarins and to UV-irradiation by the synthesis of flavone glycosides, whereas ozone treatment results in the induction of both pathways. Ozone treatment (200 nl 1−1, 10 h) of parsley seedlings results in an increased mRNA level of early genes within 3 h [pathogenesis related proteins PR1, PR2 and an elicitor-induced protein with unknown function (Eli 16)], of intermediate induced genes within 6 h [phenylalanine ammonia-lyase (PAL), 4-coumaroyl-CoA ligase (4CL), chalcone synthase (CHS)], and of late genes within 12 h [hydroxyproline-rich glycoprotein (HRGP), peroxidase (POD)]. 2D-PAGE of in vitro translated poly(A)+ RNA isolated from ozone-treated parsley seedlings revealed about 20 induced and 10 repressed translation products. A cDNA library from parsley seedlings was differential screened, yielding several induced cDNA clones. One of the ozone-induced cDNA clones could be identified as coding for PR1-1 by hybrid-selected in vitro translation and by DNA sequence analysis.

Currents were measured along two routes through Yell Sound to Sullom Voe in the Shetland Islands. Current meter moorings were deployed by the consulting engineers Peter Fraenkell and Partners for one month at 20 positions with three meters which measured the flow from near surface to a depth of 20 metres. The accuracy of these measurements is considered and the difficulty of making measurements in this region is illustrated.

The paper discusses the nature and variability of the currents that were measured and resolves the currents into a tidal and non-tidal component. An analysis procedure is developed for removing the tidal component and for producing tidal current vectors for each position. From this the general tidal circulation pattern is constructed and discussed. It is shown that tidal currents along the eastern route are too high at certain states of the tide for safe navigation.

Current surges of significant magnitude are shown to exist throughout the area. These are driven by the tidal motion and it is suggested that they are an effect of travelling gyres which are generated in the lee of islands and shallow banks when the tidal streams are largest.

For a full decade, the Office of Naval Research (ONR) led the United States into the development of science by research contract. Marine geophysics and oceanography were a part of this, as were the solid earth sciences and meteorology.

By 1950, ONR was firmly established, World War II seemed far behind, and oceanographers in the United States were enthusiastically looking forward to what turned out to be ten years of their most productive work. By combining oceanographic talent and ONR funds and logistics, there was created one of the most effective systems yet invented for accomplishing science and technology at sea.

New institutions were established, old institutions revived, fleets were designed, deep diving initiated, ocean monitoring begun, Arctic oceanography started, expeditions mounted, and discoveries made which, when coupled with other knowledge, were to contribute to far-reaching consequences for the earth sciences and how we now view our geophysically active planet.

The oceanographers will speak for themselves. This paper presents only the view from Washington at the time, and how at least some of the activity there helped to make possible the Great Decade of Oceanographic Development, 1950–59.

Venoms are complex mixtures of many different components, whereas a toxin is a single pure compound whose activity can be specified. Toxins often have novel, highly specific activities. Studies on toxins open the way to design therapeutically useful molecules based on the structural information obtained from the toxins.

An example of successful drug development from a component of a snake venom is that of the inhibitors of angiotensin-converting enzyme (ACE). The first ACE inhibitors were developed from work on peptides isolated from the Brazilian arrowhead viper Bothrops jaracusa that prolonged the action of bradykinin. The venom components blocked the enzyme that inactivated bradykinin; the same enzyme activated the precursor of the vasoconstrictor hormone angiotensin. Hence, a valuable new type of therapy was established by developing the leads provided by the natural toxin.

Dendrotoxins are small proteins from mamba venoms that block rapidly activating K+ channels in neurones. There are possibilities that dendrotoxin could be the basis for drug design. A small analogue that mimicked the activity of dendrotoxin in the central nervous system might boost the activity of certain neuronal pathways. Potentially, such a compound might be able to restore some of the function of systems damaged by progressive neurodegenerative diseases. Although dendrotoxin-like compounds would not be a cure for these diseases, they may provide temporary relief from symptoms.

Conversely, compounds with the specificity of dendrotoxin but with ability to activate K+ channels, rather than block them, may be a novel way of reducing abnormal electrical activity in the brain. Hence, they may form the basis of a new type of anticonvulsant drug for epilepsies.

Recent work at Strathclyde has concentrated on defining the structure-activity relationships of the naturally occurring dendrotoxins and on synthesising small analogues of the postulated ‘active site’. Preliminary results are encouraging, and it is hoped to go from green mamba venom to dendrotoxin to therapeutically useful drugs.

The Firth of Forth, in terms of physical oceanography, is part of the North Sea. The general circulation pattern in the firth must be regarded as largely speculative. There have been insufficient measurements of insufficient quality, and what evidence exists leads to the view that what circulation there is, is sluggish and varies from season to season and from year to year.

A description is given of the three principal mechanisms that contribute to circulation. Tides, due initially to astronomical forces, manifest themselves in the Firth of Forth through the rise and fall of the adjacent open sea. This rise and fall, periodic in mid ocean, is no longer strictly so in the firth and neither are the tidal currents. The wind-driven currents in the sea are influenced by the earth's rotation. In the Firth of Forth, some of this influence is retained. Naturally, wind-driven currents are larger near the surface. Finally, when water of different densities meets, overturning causes convection currents. All of these effects are present to some extent in the Firth of Forth. In addition, specific account has to be taken of complicated coastal and bottom topography and river outflow. Some attempt to bring together these effects and available measurements is made in this paper. Lastly, several theoretical models are proposed which account for the magnitudes and directions of the observed steady circulation. Mathematical details are given in appendices.

Sands are sorted by the actions of air and water. A mathematical–physical model for the ensuing spatial and temporal variations in the size distributions of the sand grains is outlined. A crucial element in aeolian sorting and transport of sand is the process that takes place when a saltating grain impinges on the sand surface. This raises the problem of describing the texture of sand surfaces. Some initial empirical and mathematical findings concerning this problem are discussed. A closely connected question is that of how the grains in a sand deposit are packed and how this relates to the size distribution. Voronoi tesselations in combination with random point processes seem to offer one useful approach to the question.

A survey has been made of the condition of the mantle cavity in populations of Lymnœa (Radix) peregra (Müller) and Physa fontinalis (L.) living in a range of depths and habitats in Loch Lomond. In many populations, including some in relatively shallow water, the mantle cavity remains water-filled throughout life. Where the cavity contains a gas-bubble, micro-gas-analysis (using a modification of Krogh's methods) has revealed that in some cases the gas composition is such that the bubble could be used as a physical gill, while in others such use is unlikely. Other observations on respiratory behaviour of the two species are reported, and growth-changes are noted in the surfaces available for cutaneous respiration. The study is discussed in relation to previous work on the respiration and ecology of freshwater pulmonate snails.

While only in its infancy, the application of electrophoretic analysis in studying the evolutionary biology of pteridophytes is proving to be of considerable value. Since the technique identifies subtle differences in protein structure, it can generate an improved picture of the genetic composition of organisms. To date electrophoresis is (1) providing us with new information about the structure of the pteridophyte genome, (2) interfacing well with laboratory studies of breeding system mechanisms to indicate that some pteridophytes are predominantly outcrossing species, and (3) generating genome-specific markers for detecting hybrids and analysing patterns of evolution. Electrophoretic data suggest that species of Bommeria are very distinct from one another and may not be congeneric. Further, enzyme characters indicate that the sexual Bommeria species have maintained a mechanism to promote outcrossing in populations, in spite of the limitations that this breeding system places on colonising ability. In Cystopteris, electrophoretic markers are of value in deciphering species relationships and origins, especially among neopolyploid taxa. The indication in Cystopteris that extant diploids are outcrossing may help to explain the complex systematic patterns that currently exist within and among its taxa. Further investigations may demonstrate that similar mechanisms are prevalent among other systematically challenging ferns and fern allies.

Accurate quantitative assessment of the benefits accruing from the genetic improvement of crops is difficult. Crop yield increases are achieved through the introduction of new, improved varieties, through improvements in cultural practices and as a consequence of interactions that occur between new varieties, cultural practices and environmental conditions. Part of the yield increases from new varieties is as a consequence of genetic plant resistance to pests and diseases. Plant breeding, which is dependent on there being available a wide relevant genetic base for each crop, has also provided considerable improvements in quality, as well as improving adaptability to a wider range of environments.

In the developed world estimated annual yield increases from the genetic improvement of crops, especially cereals, are of the order of 1–2%. Examples are given from a number of crops of hybrid varieties, of varieties with improved quality and of varieties that are genetically resistant to pests and diseases to illustrate that conventional plant breeding, allied to multi-disciplinary, strategic research, has been very effective, both economically and in protecting the environment.

The Race A/Race B hybrid females of D. pseudo-obscura have a high percentage of fertility, comparable with that of females of pure race. The number and viability of their offspring, however, are largely affected by the genetic constitution of the hybrid female as well as by that of the male to which she is mated in the backcross. Hence the performance of any given hybrid is determined in the first instance by the actual strains of the pure races which are used in making the P1 racial cross. Generally speaking the results are of the same order whenever the same strains are used. The progenies of hybrid females of different genetic constitution may differ in three main aspects: (1) The total number of offspring may be comparable with that usually obtained in a pure race cross; it may be reduced to any extent; in certain matings it is consistently at zero. (2) The sex ratio may be completely normal or male-deficient or female-deficient in any degree; completely uni-sexual progenies are sometimes obtained. (The above observations are mainly in agreement with reports of earlier writers; cf. Lancefield, 1929, Dobzhansky, 1936, Mampell, 1941, Sturtevant, 1937.) (3) “Viability characters,” i.e. those affecting general vigour and physical normality, may be of a high or a low grade; some progenies are comparable in this respect with the pure race, the only exception being that they show a much greater range of variation in body-size of both sexes, and in the testis size of males, abnormalities which are common to all back-cross progenies whatever the genetic constitution of the mother or father. Some progenies show in addition deformities of a peculiar type usually affecting the abdomen and occasionally the legs and wings.