Caryedon gonagra (F.) is a beetle pest in ground nut kernels and occurs in this country in stored nuts. The karyotype has been investigated in both sexes. The chromosome complement of 2n = i8 includes a heteromorphic sex-determining pair—a large metacentric X and a small spherical Y. Particular attention has been paid to the sex bivalent in the male since study of this character alone may prove sufficiently diagnostic in species separation in closely related members of the Bruchidae.

The distribution of about thirty species of warm water siphonophores over the period 1947–1964 to the north-west and north of the British Isles is used to give a generalized picture of the path of the Lusitanian stream. These species, which originate much further south, are relatively intolerent to change of environment and the distances they are carried can be associated with the degree of inflow on a yearly and seasonal basis.

Grouping the findings into four series of years over the 18 year period shows an increase in their northerly distribution from 1947 reaching a maximum in 1953 and 1954. This has since been maintained, with annual variations, at least until 1963. It is hoped that the data presented here can be used when comparing future studies of climatic change with the distribution of water masses.

The studies on the epidemiology of yellow fever which have been carried out in Africa in the period 1925–1966 are presented in narrative form.

The original isolation of the virus is described, leading on to the survey work which showed that the infection is widespread in tropical Africa and that monkeys are very important hosts—perhaps the definitive mammalian hosts—of the virus. The discoveries of a monkey-to-man cycle in which the classical vector mosquito, Aedes aegypti, is replaced by A. simpsoni and of a monkey-to-monkey cycle, in which A. africanus is the vector, are described.

Recent epidemics are discussed, particularly that in Ethiopia, where there were about 200,000 cases, with 30,000 deaths, in the period 1960–62 and where the principal vector in the man-to-man cycle was A. simpsoni.

Work on groups of animals other than monkeys is reviewed, with particular reference to studies on the lemuroid Primates of the genus Galago, which are believed to be natural hosts of the virus. It is concluded that there are still many unknown facets in the epidemiology.

The title to the talk this afternoon, “Abiogenic Information Coupling, or, How protein and DNA were married”, is, indeed, an excerpt from the much broader subject to which your President referred, namely chemical evolution of life on the surface of the earth, with some speculation about elsewhere as well. Actually, the “elsewhere” portion is more than a hopeful addition because it may provide a check on the speculations on the origin of life on the surface of the earth, which is very difficult to obtain inany other way.

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.

Organic acids are working solvents for a number of proteins, notably the collagens. The mechanism of solubilization can be assumed, as a first hypothesis, to consist of a weakening of salt bonds such that chain-chain interactions are lessened and dispersion can occur. However, this cannot be exclusively true since, in the case of the collagen, it has been pointed out (Gustavson 1956) that this protein is soluble in acetic acid (pK=4·76 at 25°C.) and citric acid (pK1 = 3·13; pK2=476; pK3=6·39, at 25°) but not in hydrochloric or mineral acids of equivalent or greater hydrogen ion concentration. The hydrogen ion is thus not the dominant solubilising factor. The same author suggested that the unionized organic acids were bound by peptide bonds of proteins in such a way as to wedge apart the associated chains.

This discussion of the biochemical lesions produced in animal cells by ionizing radiation will to all intents and purposes be restricted to a consideration of the immediate response to doses of 1000 rads or less in two rat tissues only, namely the thymus gland and the regenerating liver. The experiments we have carried out with these two tissues have led us to the view that in these organs the ultimate damage to the cell stems from an initial upset of the nuclear thiol-disulphide equilibrium.

The definition of the name “kylite” is reviewed and it is suggested that its usage should be discontinued. What is now emphasised as the criterion of most importance in distinguishing “kylites” from crinanites and teschenites is the development of a strongly zoned purplish pink augite in advance of feldspar. Basic alkaline doleritic rocks in which the augite develops in this manner could be referred to simply as kylitic. Specimens were systematically collected from the picritic sill near Dalmellington which is kylitic in type. Rocks from different levels in this sill have been chemically analysed, and also unzoned olivine (Mg74.4) and zoned augite. A vein (and the augite from it) in the kylitic sill near Troon, known as the Hillhouse Quarry Sill, have also been chemically analysed. The chemical compositions of all these analysed rocks and of the analysed augites are compared with appropriate data from, in particular, the sills of the Shiant Isles and Lugar, and the Black Jack Sill in New South Wales. Some relationships of kylitic rocks with the differentiation trends in these sills are briefly discussed with the aid of variation diagrams. On the basis of the available evidence it is inferred that in the olivine-rich Dalmellington Sill, olivine has accumulated prior to intrusion and that subsequent “flowage differentiation” has apparently been inoperative.

The study of chromosome aberrations produced by the irradiation in vivo of men dates from 1960, and nearly all the work has been done on cultures of blood in which lymphocytes respond to phytohæmagglutinin by synthesising DNA and then dividing (Moorhead et al. 1960). This technique can now be used on a moderately extensive scale and it is possible to trace the pattern of events after a single exposure or repeated exposures to radiation involving either the whole or part of the body, whether the exposure be for therapeutic purposes, or from the explosion of a nuclear weapon, or accidentally received, or incurred for occupational reasons. We can now detect the effect of radiation in producing an increased number of lymphocytes in the peripheral blood with chromosome aberrations with quite low doses of radiation, for example an occupational dose of about 15 to 20 rads. accumulated over a few years or the doses received during fluoroscopic procedures in diagnostic radiology. For the future we anticipate that the development of automated techniques of chromosomes counting and analysis will permit quantitative work down to such levels and perhaps even lower.

Classical immunology grew out of the observation that patients who recovered from certain infectious diseases like plague and smallpox rarely contracted the same disease again. The early development of the subject was largely stimulated by the fact that many patients died during the initial attack, and the consequent need for developing methods of prevention, diagnosis and treatment.

The passive electrical impedance characteristics exhibited by the body during rectangular pulse stimulation are analysed, and typical observed properties are specified in terms of the parameters of an equivalent electrical circuit. Equations are derived which describe the current waveform generated in such a circuit by a rectangular pulse stimulator of known finite output impedance. The response of nerve to currents of this form is analysed, and equations are derived which permit the comparison of threshold and intensity-duration data obtained with stimulators of different output impedances. Results predicted by the theory are shown to be in good agreement with experimental results.

Adult powan, Coregonus clupeoides Lacépède, in Loch Lomond show regular diurnal and seasonal migrations, connected normally with either feeding or reproduction. As the breeding season approaches, most of the adult population gather in deep water (usually in the vicinity of the areas of wave-washed gravel and small stones in shallow water, which form the main spawning grounds). The male fish start to move on to these grounds nightly towards the end of December each year; at the end of this month, but mainly during January, the females ripen and join them for spawning. This is completed by the beginning of February and the population then gradually disperses over the rest of the loch. The present fecundity estimates, carried out for female powan during two seasons, are in general agreement with those found for Coregonus elsewhere in the Palearctic region. They give an average of 5750 eggs per adult fish, the mean fork length of which was just over 27 cm. Though there is a positive correlation between the numbers of eggs produced and the size of the females, it is not a strong one. After being laid, the eggs immediately undergo a heavy mortality and are eaten in considerable numbers by trout, Salmo trutta L., powan, roach, Rutilus rutilus (L.) Phryganea larvae, and various other animals. The adult powan too are preyed upon extensively at this time in certain parts of Loch Lomond by pike, Esox luciusL. The reproductive ecology of the powan shows several basic similarities to that of other Salmonidae in the British Isles, the main features fitting well with what has been postulated about the origin and distribution of the family in this country.

It Is the general object of this paper to consider which of the many actions of anti-lymphocytic antibody contribute to its immunosuppressive action. However, it will be principally concerned with the kinetics of lymphopoiesis in mice receiving anti-lymphocytic antibody and the relevance of this activity to the resulting immunosuppression.

The breeding season of Hypogastrura viatica (Tullberg 1872) appears to reach its peak in mid-April when both sexes occur in about equal numbers. Cytological examination reveals a karyotype of 14/XX in the female and 13X/O in the male. The investigation of spermateleosis and maturation of the egg is incomplete but arguments for and against the occurrence of parthenogenesis are presented.

The experiments to be discussed here all involve the irradiation of cells in early interphase and the observation of these cells, or rather their chromosomes, at the first mitosis following radiation exposure. The irradiation of such G1 cells results in the formation of chromosome-type aberrations that are a consequence of breaks or exchanges involving the whole chromosome, both chromatids being affected in exactly the same way and at identical loci. These chromosome-type aberrations are of various kinds and a large proportion of them are very easy to detect cytologically. The four main types that are normally studied by cytologists, since they can be easily and objectively scored, are the terminal and interstitial deletions and the dicentric and ring aberrations (see text-fig. 1).

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.

Past studies of the relationships between different populations of Coregonus have demonstrated the great plasticity of form exhibited by this genus throughout the Palearctic region. In addition to standard morphological accounts, hybridization and rearing studies are important in attempting to assess the relationships between different races, and this paper describes some initial work which has been carried out in this direction. The development of eggs of the Loch Lomond powan, Coregonus clupeoides Lacépède, has been studied in the laboratory and shown to follow a definite pattern. The average incubation period at 6–9° C is 65 days though considerable variation in this time occurs. Eggs and sperm kept separate and without water still showed 50 per cent fertilization after 3 days but none after 6 days. Hybrids of two races of Coregonus, one living in Scotland the other in Wales, were produced by bringing together eggs and sperm which had been kept cool and dry during transport. The value of these experiments in relation to past and future research is discussed.

As the three previous papers in this Symposium have shown (Ord and Stocken 1968; Evans 1968; Court-Brown 1968) the exploration of radiation effects within the cell has its own intrinsic fascination quite apart from its relevance to an understanding of the phenomena which may be observed after irradiation of the complex organism, vertebrate or invertebrate. Whitmore (cf. Whitmore Gulyas and Botond 1965) has been one of the pioneer workers on a previously unsuspected phenomenon, the quantitatively substantial recovery of the ability to divide which occurs within the first hour or two after exposure to low LET radiation. In cultures of mammalian cells in vitro this kind of recovery was shown to have nothing to do with cell division, to occur at all stages of the cell cycle, and to be little, if at all, affected by a reduction in temperature which would be expected a priori to modify profoundly the rate of chemical reactions. Whitmore's technique for synchronising asynchronously dividing cell cultures by the selective suicide of DNA synthesising cells following the incorporation of radioactively labelled DNA precursors with high specific activity has a wide application (Whitmore and Gulyas 1966). Workers from his laboratory have proposed an interesting approach to the real meaning of “ability to divide” and “recovery” based on the idea that there is a certain probability of failure at each cell division and that this probability may be permanently increased by exposure to radiation (Till, McCulloch and Siminovitch 1964). Thus radiation damage may be expressed by failure of cell division not only at the first or second divisions after exposure but also at any subsequent division in the distant future.

During recent years the heterogeneity of equine antibodies to a variety of antigens has been convincingly demonstrated (Rockey, Klinman and Karush 1964; Raynaud, Iscaki and Mangalo 1965; Allen, Sirisina and Vaughan 1965; Klinman et al. 1966; Klinman and Karush 1967; Johnson and Allen 1968). For example, extensive studies on equine anti-hapten antibodies have shown that the IgG fraction of horse serum contains at least four different proteins, namely the IgGa, IgGb, IgGc and IOS IgG globulins in addition to the IgG(T) and IgM proteins (Rockey et al. 1964; Klinman et al. 1966). These antibodies differ widely in their ability to precipitate the protein-bound hapten and to fix complement, and their concentrations and binding affinities vary considerably during a course of immunization (Klinman et al. 1966).