bluuebunny/crossref_metadata_2025 huggingface dataset:
ON THE DEVELOPMENT OF FEATHERS
Authors: LILLIE FRANK R.
Published: January 2008

I. Feather papillae are regarded as individually persistent throughout life, from the time of their origin between the sixth and ninth days of embryonic life. In each feather tract the order of origin is significantly related to dynamic field properties of the tract, such as growth rates, degrees of asymmetry, etc.

2. Recent work on the anatomy and development of the rhachis with special reference to barb relations and the independent origin of the central rhachis is considered; also the development of the after‐feather and of the pulp and its blood supply.

3. By plotting axial growth and isochrones on the vane of the feather it is possible to relate any definitive locus to its time and place of origin in the germ, and hence to the conditions of its determination.

4. The papillae of definitive feathers may be transplanted, or subdivided, or parts of papillae of different tracts may be recombined. The results of the operations show that papillae have a definitive bilateral organization, like amphibian eggs, for example; that they are tract‐specific; and that a dorsal field, including the central rhachis, exerts a dominant influence on development. Various abnormalities of feather form produced may be interpreted. Twins and chimaerae may be produced. Abnormalities artificially produced persist through successive generations of feathers from the same follicle. The mesoderm of the papilla is regarded as the seat of the initial inductions.

5. The melanophores of feather germs are derived from the neural crest. When transplanted to foreign fowl hosts they determine the donor pattern in the host, as, for instance, barring in a white host. The genotypic composition of the donor melanophore is the controlling factor in both colour and pattern of the host feather in these experiments in all breeds of fowl examined.

6. The growing feather germ is a very sensitive indicator; reactions may be read by pattern modifications in the finished feather and referred to their locus of origin in the germ (cf. no. 3).

7. The thresholds of reaction of feathers to female hormone increase in proportion to rates of axial growth. This is very conspicuous with reference to the discontinuous rates of different tracts, and is also to be observed with reference to gradations of growth rate within a single tract.

8. Within the individual feather germ of breast and saddle tract, threshold of reaction to female hormone and thyroxin rises from dorsal to ventral loci of the collar. These transverse gradients produce transverse patterns on the vane of the feather varying in form according to rise and fall of hormone in the blood stream by absorption and excretion after injection: the principle of rate of reaction which is inversely proportional to threshold is also a factor in the determination of pattern.

9. The principles of physiology of development may be applied to some problems of physiological genetics, as, for instance, in the case of barred patterns.
THE NUMBER CONCEPTION IN ANIMAL PSYCHOLOGY
Authors: HONIGMANN H.
Published: January 2008

1. The first attempts to approach the problem of number conception in animals consisted in a training to identify one object out of many by its relative position.

2. The multiple‐choice method, although an advance on previous work, has yielded relatively poor results. The only apparent exception, namely the striking results obtained with finches, is probably due to a technical error.

3. Experiments with a temporal maze have shown that it is extremely difficult for animals to perform a double alternation, and no animal has yet been trained to perform this more than once successively. Claims that some birds are able to select every third out of a line of similar objects are without convincing foundation owing to the lack of adequate control tests.

4. The experiments of Verlaine and his collaborators led to the belief in a genuine number conception in animals, but the lack of satisfactory controls deprives the results of these cleverly devised experiments of validity.

5. Bierens de Haan repeated these experiments on a sound basis with the necessary controls. He found that the animals trained themselves to perform two or three single actions in a certain rhythm, and that consequently increasing the intervals between the single actions destroyed the training.

6. Systematic investigation of the two basic abilities of performing an action a certain number of times and of discriminating between two quantities of objects gave the interesting result that the limit in both cases is respectively 6 or 5:6 for all animals investigated. The discrimination between 6 and 7 has never been achieved.

7. Experiments with parrakeets gave better results than with pigeons, but both groups were surpassed by the achievements of jackdaws. The latter were able to learn four different kinds of number training, and to make use of them simultaneously. They could also to a certain extent combine both basic abilities. But a close analysis of these surprising accomplishments shows that even here any counting or number conception in the human sense of the word does not exist.
NUCLEAR and SOMATIC PHASES IN THE FLORIDEAE
Authors: DREW KATHLEEN M.
Published: January 2008

(i) The need for a considerable extension of morphological and cytological work in the Florideae is pointed out. (2) Before proceeding to the survey current terminology is reviewed; some terms are discarded and definitions are given for those retained. The survey shows that our cytological knowledge is limited almost entirely to two of the six orders, the Nemalionales and Ceramiales. Members of the Nemalionales show great variety as regards the somatic phase sequence in the life history. Species investigated cytologically, to varying degrees of detail, are all of the Nemalion type, that is, two morphologically dissimilar haploid phases separated by a very short diplophase of the nucleus. The Gelidiales have been completely neglected, and apart from Corallina officinalis var. mediterranea so have the Cryptonemiales. In this latter order there are indications of ‘atypical’ phase sequence. This is also true of the Gigartinales which include in addition forms showing the Phyllophora Brodiaei type of life history, i.e. two morphologically dissimilar phases, one a gametophyte and the other a tetrasporic nemathecium developed from the auxiliary cell. The nuclear phase sequence is unknown. Information about the nuclear history in the Rhodymeniales is only sufficient to indicate problems in need of investigation. In the Ceramiales the Polysiphonia type of life history with three somatic phases (two morphologically similar) and two nuclear phases appears to be general, and detailed accounts of such exist for several species. Other types are known and representatives have been investigated: Spermothamnion Turneri has been shown to be cytologically polyphasic and to be characterized by the formation of functional sexual organs on the diploid; the polysporangium of S. Snyderae has been shown to be a compound tetrasporangium, and Plumaria elegans has been found to have three nuclear phases, the triploid bearing a special type of sporangium. In addition, some species show unusual somatic phases sequences, the nuclear phases being unknown. (3) Three lines of cytological research are envisaged associated with ecological and physiological investigations. (4) There is a striking absence of physiological concepts concerning the Florideae and hence the need for pure culture and general physiological investigations.

I wish to express my thanks to Prof. C. W. Wardlaw for his stimulating interest and help in the preparation of this article, and also to the Council of the University of Manchester for library facilities. Thanks are also due to Mr E. Ashby for his help in the production of the figures. Owing to war‐time restrictions direct copying of previously published figures has not been possible. Instead they have been photographed and magnified considerably in order that the photographic image could be meticulously picked out in Indian ink. Subsequently the diagram was cleared by bleaching and reduced to its original size. I trust that faithful copies of the originals, as published, have thus been obtained.
THEORETICAL ASPECTS OF BACTERIAL CHEMOTHERAPY
Authors: MCILWAIN HENRY
Published: January 2008

Higher organisms and micro‐organisms exhibit many types of mutual action and association, and that type of interaction in which the micro‐organism becomes a parasite is normally prevented by the potential host. If parasitism is established its course may be impeded by administration of substances to the host; interaction in the resulting system of drug, parasite and host then constitutes chemotherapy.

The interactions of successful bacterial chemothera‐peuticals with the parasites, apart from the host, show characters which in most cases afford a basis for their effects in vivo. Their action may be to retard bacterial growth, as is the case with sulphonamides. They may stop the use by the parasite of substances which protect it from the host, as do the antipneumococcal polysaccharidases; or they may react with bacterial products which are injurious to the host, as do antitoxins. Such actions are susceptible to further analysis. The effects upon growth have been found to be associated with particular substances whose nature in several cases has suggested the mode of action of the inhibitor. Hypotheses based upon such findings have enabled certain new types of agents to be prepared, and reasons given for their structural specificity. Processes of the parasite, which are affected by chemotherapeuticals, have also been characterized by following the influence of the agents upon the course of growth of the parasite. A beginning has been made to specifying such influence in terms of effects upon isolated metabolic processes and other events in the parasite.

Interaction of the host with both parasite and antibacterial agent or potential agent condition the issue in chemotherapy. The concentrations of effective agent reached at different times in different parts of the host depend upon characters which are open to experimental modification, such as the mode of administration of the agent, but also upon many which are not. The latter may be accommodated by suitable choice or design of agent and include its physiological characters such as absorption, excretion and reabsorption, and biochemical ones such as its activation or inactivation by substances or processes of the host. It is necessary to study these factors, and other undesirable reactions with the host, before correlation of chemotherapeutic efficacy with structure of the agent can be expected. Events in the complete chemotherapeutic system have been referred to properties of its components by observations which include: correlation of the actions of an agent upon the parasite in vivo and in vitro; the reproduction in vitro of synergism and antagonism observed in chemotherapy; the finding of in vitro phenomena associated with drug resistance in vivo; and the type of change in the host associated with success of chemotherapy or with normal recovery from, and resistance to, infection.
BACTERIAL GROWTH
Authors: HINSHELWOOD C. N.
Published: January 2008

(i) The structure of the bacterial cell is simple: the various regions of enzyme activity may be macromolecular networks of specific pattern which grow by poly‐condensation reactions. Intermediate substrates diffuse from one enzyme to another in the cell, so that the activity of the bacterium is at least in part a sequence of chemical reactions linked both temporally and spatially in definite relations. Various growth phenomena can usefully be looked at from this point of view. A fundamental scheme of enzyme synthesis is considered. (2) The various phases of the bacterial growth cycle are considered. During the lag, among other events, concentrations of diffusible intermediates are built up: these intermediates may be lost from the cell (which accounts for various observations, including an effect of inoculum size on lag). The starting‐point of the reaction series varies with the species of bacterium. When all enzymes are active, and all the intermediates are present with stationary concentration gradients, the logarithmic phase begins. The conditions determining the validity of the logarithmic growth law, the factors governing the setting in of the stationary phase, and the law expressing the decline of the viable population are discussed in the light of experimental data. (3) Cell elongation and cell division are factors separately modifiable by media or by drugs, with resulting changes in morphology. In particular the formation of cells of abnormal length is considered. ‘Life cycles’ are not accepted. (4) The laws expressing the influence of drug concentration on bacterial growth are discussed. Drugs may attack specifically different points in the reaction sequence: they may influence lag and growth rate independently. The action of proflavine on a coliform organism is considered in some detail. (5) The adaptation of bacteria to use new sources or to resist drugs is thought to depend upon modifications induced. in individual cells during growth, and not to be explicable simply by a selectionof substrains. (6) Various groups of experimental facts are described and the hypothesis put forward that certain adaptation phenomena arise from a modification of the relative proportions of different enzymes, occurring during the expansion of the cell substance. The possibility that variants arise from multiple modes of cell division is also considered: change of enzyme balance and multiple modes of division are probably interrelated effects. (7) The spontaneous and induced reversion of drug adaptation is considered. (8) The limits of adaptation and the reason for the stability of the main species characters is discussed.
THE FLORISTIC COMPOSITION OF PRIMARY TROPICAL RAIN FOREST
Authors: RICHARDS P. W.
Published: January 2008

(i) The tropical rain forest is a formation‐type or pan‐climax. Its outstanding characteristic is the enormous wealth of species of which it is composed. (2) The investigation of the floristic composition of the rain forest presents special difficulties owing to the inaccessibility of the tree‐tops, non‐seasonal flowering and the backward state of taxonomy in tropical regions. For these reasons little definite information has been forthcoming on the subject until recently and the rain forest in each of the main geographical regions has been regarded as forming a vast assemblage of species varying in composition from place to place and not differentiated into distinct forest types comparable to the associations and consociations of temperate forests. (3) The floristic composition can best be studied by counting the trees on sample plots, identifying them first of all by their vernacular names with the help of native ‘tree‐finders’. With sufficient precautions this method can be made to give results of scientific value. (4) Primary lowland rain forest may be either Mixed Forest with numerous dominants or one dominant may form a large proportion of the stand. (5) Mixed rain forests may contain up to 100 species of trees 8 in. diameter and over in a sample plot 400times400 ft. The majority of the species in such a plot are represented by one or very few individuals, the average number of individuals per species (Mischungs‐quotient)for trees 8 in. diameter and over being sometimes as low as 2–7. The evidence suggests that in any one geographical area there is only one mixed association whose composition fluctuates in both space and time. (6) Forests in which one species forms a large proportion of the whole stand are found in all the major tropical regions, but occupy small areas compared with the mixed associations. Some of these single‐dominant types are comparable with the consociations of temperate forest climaxes, while others should probably be regarded as societies of a gregarious species. In South America and Africa the majority of the dominants of consociations belong to the Leguminosae. (7) Most, perhaps all, of these single‐dominant communities occupy special soils or habitats and it is suggested that they tend to be restricted to non‐optimal soils while the mixed association occupies optimum soils. On similar soils in geographically widely separated areas there tends to be a parallel differentiation of edaphic forest types. (8) The single‐dominant forests can probably be regarded as what Braun has termed ‘association‐segregates’. If this is so the tropical rain forest, like the ‘Mixed Mesophytic Forest’ of North America, would consist of undifferentiated climax associations together with association segregates which are consociations, i.e. associations with a tendency to single‐species dominance.

I would like to express my gratitude to Mr T. A. W. Davis and Mr T. G. Tutin for communicating unpublished data, and to Dr H. Godwin and Mr T. G. Tutin for kindly reading and criticizing the manuscript.
THE ROLE OF THE NERVOUS SYSTEM IN SOME ACTIVITIES OF STARFISHES
Authors: SMITH J. E.
Published: January 2008

(i) The general disposition of the sensory, association (internuncial) and motor elements of the starfish arm as revealed by intra‐vitam staining is described and figured (Fig. i), and (2) the nature of the nervous arcs responsible for reflex activities is discussed. (3) It is pointed out that the nature of the activities of an organ and the degree of integration of groups of organs are conditioned by the form and properties of the neurones and tracts through which they are innervated. (4) The pedicellariae, papulae and spines which are situated on, or are part of the dorsal body wall of a starfish are innervated through a plexus which has peripheral qualities. (5) There is little evidence of anatomical differentiation within the peripheral plexus except for the presence of groups of transversely running tracts which may correspond to the through‐conduction tracts (vide infra (8)). (6) The properties of the peripheral plexus are those of a nerve net as defined by Pantin (1935a, c) and the movements of the pedicellariae are analysed in relation to these properties. (7) The net shows evidence of differential capacity for facilitation in its various parts, in particular (8), there are transverse through‐conduction tracts in the plexus which, when coupled with the lateral motor systems of neurones (E of Fig. i) are the means of innervating the papulae and muscles of the body wall. (9) The movements and postures of the tube feet are described. (10) Together with the capacity of the feet to be co‐ordinated throughout the entire animal they demonstrate the central nervous properties of the circumoral ring and radial cords through which they are innervated. (11) These central nervous properties derive from the presence of special centres of co‐ordination, from a marked polarity of conduction, and from a certain configuration of the motor neurones within the central nervous system and the tube feet. (12) An account is given of the probable location and functions of the nerve centres and of the disposition of the nerve tracts within the central nervous system. (13) A brief reference is made to the effects of peripheral excitation on the pattern of coordinated movement of the podia.
THE PRESENT STATUS OF THE GERM‐CELL PROBLEM IN VERTEBRATES
Authors: EVERETT N. B.
Published: January 2008

(i) Morphological studies relating to the origin and differentiation of the definitive germ cells in vertebrates have, as indicated, resulted in conflicting views. In many instances two or more competent investigators who have studied the same form have reached different conclusions. (2) Some contend that the germ cells are set aside from the soma during the early stages of embryonic development, and that these alone serve as the progenitors of the functional sex cells. (3) Others recognize an early differentiation of sex cells but hold that these are supplemented by others produced from the somatic epithelium of the gonad in late embryonic or post‐embryonic stages. (4) Another group recognizes the early differentiated cells as germ cells but contend that these all degenerate and that the definitive ones are formed from the germinal epithelium. These degenerating germ cells are believed by certain authors to be a phylogenetic recapitulation of the condition in lower forms. (5) Finally, yet another group contends that the so‐called primordial germ cells are not germ cells at all but are enlarged cells in some stage of mitosis or in some specific metabolic phase. This group believes that all germ cells are derived from the somatic cells of the germinal epithelium. (6) Experimental work supports the view that the primordial germ cells, which are recognized early, are the progenitors of the definitive sex cells. When these primordial germ cells are prevented from reaching the site of the developing gonad the individual fails to develop sex cells, although a sterile gonad and its associated structures may develop. (7) I suggest that the observed proliferation of germ cells from the germinal epithelium, reported by numerous investigators, can be interpreted in another way by a thorough study of the enlarged germ cells in relation to the epithelium. It seems probable that the cells of the epithelium, which form functional sex elements, are not and never were a part of the mesothelial covering, but are cells which were segregated early, and are merely stored in the epithelium.
THE PHYSIOLOGICAL SIGNIFICANCE OF INORGANIC LEVELS IN THE INTERNAL MEDIUM OF ANIMALS
Authors: CONWAY EDWARD J.
Published: January 2008

(i) Proceeding from a consideration of the non‐diffusible constituents of the cells, the sum of the electric charges thereon, the mean intracellular pH, and an optimum or maximum membrane potential, the inorganic levels of Na, K, H, HCO2 and CI can be interpreted as physiological requirements and HCO3 and CI concentrations in turn, assuming a necessary ventilation tension of CO2. (2) Omitting considerations of the membrane potential, or treating them as of secondary importance, the optimum pH value, and in turn the K and HCO3 concentrations, are theoretically deducible by an alternative method of wider implications. (3) Including the effects of contact with the solid bone salts the concentration of the inorganic phosphate ions and minimal values for Ca and Mg ionic concentrations may also be deduced.
ANTIGENS, ANTIBODIES AND GENES*
Authors: IRWIN M. R.
Published: January 2008

This article is a survey of a few pertinent findings about antigens as they occur in one species of bacteria, the pneumococcus, and in the cells and organs of mammals and birds. The main points of general biological interest emphasized are as follows: (1) The fact that carbohydrates, not proteins, are responsible for the specificity of the different types of pneumococci points the way to a comparable concept of specificity in organisms other than bacteria. That is, substances other than proteins, if linked to proteins, may account for some part of known specificities. (2) Changes within each type of pneumococcus may take place from a smooth, capsulated form to a rough, non‐capsulated form, and vice versa. Under certain conditions a rough form of one type may be changed to the smooth form of an entirely different type. The activating principle in one such change has been found to be a nucleic acid. (3) The antigens of the blood cells of man are gene‐determined. There are, however, antigens of the blood cells, tissues or organs of other species which have not yet been explained genetically. (4) It has been possible by immunological techniques to make a sharp distinction between the cells or sera of closely related species. Reagents prepared by absorbing the antisera to the cells or serum of one species by the corresponding antigens of the other were reactive with the homologous antigen, but not with that used in the absorption. From these results it may be deduced that each species possesses ‘species‐specific’ antigens in comparison with a related species, as well as those common to the two species. (5) In bird species which produce viable hybrids the antigens have been found to be gene‐controlled. (6) The cellular antigens are generally thought to be the more or less direct products of their causative genes. However, a few instances are known of cellular antigens which are the result of complementary action of genes. Also, within the group of genes which act directly on the respective antigens there appear to be some which singly are capable of effecting the same combination of antigens as two (or more) alleles may produce.
THE PHYSIOLOGICAL SIGNIFICANCE OF THE PHOSPHOMONOESTERASES
Authors: MOOG FLORENCE
Published: January 2008

Researches of the past ten years bearing on the physiological significance of the common acid and alkaline phosphomonoesterases may be summarized in the following facts and concepts, (i) The alkaline phos‐phomonoesterase appears to be a salt‐soluble, the acid a water‐soluble, substance; both consist of a metallic coenzyme and a protein‐like carrier. Neither depends oh sulphydryl groups for activity, but the alkaline phosphatase seems to require amine and phenolic hydroxy! groups; it is affected only by strong oxidizing agents. There is not yet any incontestable evidence that alkaline phosphomonoesterases of different sources are not identical. (2) Phosphatases probably catalyse only hydrolyses, not syntheses. (3) The content of both phosphatases in the blood serum is characteristic of age and physiological state, and is used in the diagnosis of bone and liver disorders; biliary obstruction results in elevation of serum alkaline phosphatase probably because phosphatase is normally excreted by way of liver and gut, but other explanations are possible. Diet influences serum alkaline phosphatase level. (4) The study of phosphatase function has been advanced by the development of techniques for the histochemical demonstration of acid and alkaline phosphatases. (5) It is certain that alkaline phosphatase is indispensable in normal ossification; it is generally instrumental in abnormal calcifications, but in a few cases calcification occurs without it. (6) Glycolysis seems to accompany normal bone formation, but this fact does not clarify all the unsolved problems of ossification. (7) Hormones and vitamins influence both alkaline phosphatase activity and bone formation. (8) In kidney tubules alkaline phosphatase probably functions in dephosphorylating sugar molecules that are removed from the tubular fluid by phosphorylation. The enzyme is present at other sites where it might serve in a similar manner. (9) Phosphatases are commonly found in the cytoplasm of growing, regenerating, and secreting cells in which protein synthesis is being carried on; there appears to be a correlation in such cells between content of pentosenucleic acid and of phosphatase. In dividing nuclei, phosphatase parallels desoxyribonucleic acid. (10) Acid phosphatase is found in seminal fluid, and may help to nourish the sperm. (11) The occurrence of two common phosphomonoesterases with widely different pH optima may indicate a mechanism for allowing two dephosphorylating steps to go on simultaneously in a single cell. In tissues which carry on much traffic in glycogen, acid phosphatase is possibly provided to prevent bone formation. (12) The actual role which the phosphatases play in the physiology of the organism will be understood only with elucidation of the complete enzyme systems of which the phosphatases are a part.
LES AFFINITÉS DES GRAPTOLITHES
Authors: KOZLOWSKI PAR ROMAN
Published: January 2008

L'article contient un exposé succinct de principaux faits qui plaident en faveur d'une parentéétroite entre Ies Graptolithes et les Ptérobranches. Un examen critique est tout d'abord fait des arguments sur lesquels s'appuyaient différents auteurs pour attribuer les Graptolithes soit aux Hydroídes, soít aux Bryozoaires. On conclut que ces opinions ne reposaient pas sur des fondements solides. A l'attribution des Graptolithes aux Hydroídes s'oppose leur symétrîe nettement bilatérale, la présence à l'intérieur de leurs thèques d'un stolon à parois chitineuses ainsi que leur faculté dépaissir leurs thèques à l'extérieur. L'hypothèse, soutenue par Ulrich et Ruedemann, de la parentéétroite entre les Graptolithes et les Bryozoaires est également écartée et les arguments mis en avant par ces auteurs à l'appui de leur thèse sont considerés comme non convaincants. La théorie de l'affinité entre les Graptolithes et les Ptérobranches, développée entre 1905 et 1910 par Schepotieff et qui n'a pas trouvé d'accueil bienveillant des specialistes, est reconnue comme étant juste dans son essence, malgré l'argumentation souvent erronée de cet auteur. Une interpretation nouvelle est donnée des similitudes entre les particularités de structure des constructions chitineuses dans ces deux groupes d'animaux, appuyée surtout sur des faits nouveaux mis en évidence par létude des Graptolithes du Tremadoc de Pologne. Les rhabdosomes des Graptolithes, surtout ceux de l'ordre des Dendroidea, sont construits essentiellement de la même façon que le sont les cæneciums de Cephalodiscus et surtout le tubarium de Rhabdopleura. Tous ils se composent d'un assemblage de petits segments chitineux ou fusellus. En outre le stolon des Graptolithes est, quant à sa structure et son rôle biologique, identique à celui de Rhabdopleura. Le mode de bourgeonnement des individus de la colonie de Rhabdopleura est le même que celui de la première thèque des Graptolithes. Si Ton considère que toutes ces similitudes concernent des caractères bien spéciaux, ne se retrouvant que chez les Graptolithes parmi les animaux fossiles et chez les Ptérobranches parmi les animaux actuels, on ne peut pas échapper à la conclusion de l'existence d'une étroite liaison génétique entre ces deux groupes d'animaux, dont l'un s'est éteint aux temps paléozoïques et l'autre, qui y était également représenté, s'est continué jusquà nos jours.
THE CLASSIFICATION OF FERNS
Authors: HOLTTUM R. E.
Published: January 2008

Intensive morphological studies have been devoted to the more primitive ferns, which represent a small minority of living species, but too little is yet known about the vast majority of other ferns, with the result that recent attempts at a natural classification show considerable differences of treatment.

The problem is complicated by convergent evolution in the characters of almost all parts of a fern plant. Not only similar soral form, but also similar frond form, types of venation, scales, etc. have been developed on different evolutionary lines.

To illustrate the nature of the problem an attempt has been made to state the probable characters of a primitive leptosporangiate fern, and the kinds of ways in which existing ferns have developed from this condition. Evolutionary change in different parts of the plant has proceeded in different ways and to different degrees in the many genera of existing ferns. Primitive characters of one kind or another are shown by a great number of ferns, along with highly advanced characters of other kinds.

Recent schemes of classification are briefly compared, and a summary is given of the author's own scheme, with notes on evolutionary trends in the various groups as he sees them.

Much more information is needed on which to establish a really satisfactory scheme. The present one is put forward in the hope that others will take up the work. With modern facilities for travel, it is to be hoped that more botanists will come to the tropics and see ferns and other too‐little‐known plants in their native habitats. Morphological study needs to be undertaken with an understanding of the living plant and of its environment.
STRUCTURE and FUNCTION OF NEURONES IN RELATION TO MENTAL ACTIVITY
Authors: MONNÉ LUDWIK
Published: January 2008

1. The properties, structural, physiological and colloidal, of the cytoplasm of resting and stimulated neurones differ greatly. Jin this respect resting neurones are similar to mature unfertilized sea‐urchin eggs, which are in a depressed condition, and strongly stimulated neurones resemble fertilized sea‐urchin eggs, which are in a highly stimulated condition. The importance of this comparison for understanding the functioning of neurones is stressed.

2. The ground substance of cytoplasm is a texture of fibrils. These fibrils consist of ribonucleic‐acid‐containing chromidia and ribonucleic‐acid‐free interchromidia, which regularly alternate with one another. The structure of cytoplasm is coarse when the fibrils are agglutinated together. The chromidia, which are intensely stainable with basic dyes, aggregate with each other simultaneously with the agglutination of the cytoplasmic fibrils. The structure of cytoplasm is fine when the fibrils are separated from each other and the chromidia are consequently dispersed.

3. The structure of the cytoplasm coarsens rapidly when resting neurones of warm‐blooded animals are excised. This change does not occur when strongly stimulated neurones are excised. Coarse cytoplasmic structure and the aggregated condition of chromidia are correlated with decrease in the rate of respiration, narcosis, hibernation, sleep, and in general with inhibition of cellular activities. Fine cytoplasmic structure and the dispersed condition of chromidia are the characteristic features of chromatolysis, which occurs upon stimulation.

4. Solidifying (clotting) and liquefying enzyme systems control the properties of cytoplasm. The former enzyme system is responsible for the coarsening of cytoplasmic structure and may be activated by narcotics. Stimulation and chromatolysis are brought about when the latter enzyme system is activated. It is probable that clotting enzymes are activated in case of concussion of the brain, and liquefying enzymes upon recovery.

5. It is suggested that mental activities are depressed when the structure of the cytoplasm of neurones is coarse and that these activities are increased when this structure becomes fine.

6. Synthesis of new specific proteins may be the mechanism underlying memory. The structural changes in cytoplasm associated with thinking are probably due to protein synthesis.
CONTRACTILE and PACEMAKER MECHANISMS OF THE HEART OF TUNICATES
Authors: KRIJGSMAN B. J.
Published: January 2008

The contractile mechanism of the tunicate heart is situated in the delicate single layer of muscle fibres of the heart wall. The subsequent contraction of these fibres produces a peristaltic wave passing along the tube‐shaped heart, resulting in a true circulation. The mechanism of refilling is not yet understood.

The pacemaker system is of a diffuse nature. This basic automatism is controlled by two more powerful pacemakers, one at each end of the heart.

The peripheral pacemakers are possibly myogenic, and stimulated to contract rhythmically. These local contractions release peristaltic waves. The cause of the rhythmic activity of the pacemakers may be a metabolite which stimulates their sensory mechanism. The active pacemaker adapts itself to this stimulus, which results in a temporary arrest after a period of activity.

The fact that after such a pause the opposite pacemaker becomes active, thus causing regular reversal of pulsation, cannot be understood in terms of increasing back‐pressure. Periodic fatigue (adaptation) and subsequent restoration of the pacemakers offer a more plausible explanation of the phenomena.

Very probably the tunicate heart does not possess extrinsic regulation.

The tunicate heart is not very sensitive to ions or hypotonicity.

There is evidence that the heart possesses a special conductive system.

It has been pointed out that a number of features of the heart mechanism need further investigation.
ANTARCTIC AQUATIC ECOSYSTEMS AS HABITATS FOR PHYTOPLANKTON
Authors: PRIDDLE J. , HAWES I. , ELLIS‐EVANS J. C. , SMITH T. J.
Published: January 2008

1. The Southern Ocean is a large‐scale, relatively homogeneous upwelling ecosystem whose phytoplankton apparently grows suboptimally over much of its area. By contrast there is a wide variety of freshwater habitats in the Antarctic and in some of these phytoplankton growth efficiency is very high. The two habitats share similar temperature and irradiance regimes, but differ markedly in availability of inorganic nutrients, in grazing pressure and in the time‐ and space‐scales on which various physical processes act.

2. Concentrations of inorganic nutrients in the marine ecosystem have been represented as being in excess of phytoplankton requirements, but the ionic composition of some nutrient pools may not conform to phytoplankton preferences.

3. Nutrient‐limitation determines phytoplankton production in Antarctic lakes and gives rise to gross differences between lakes.

4. Irradiance in the water column varies greatly over the year in both marine and freshwater ecosystems. Most algae are shade‐adapted, with the ability to utilize low irradiance but with sub‐optimal response to high irradiance. However, local phytoplankton maxima may attain very high carbon fixation and growth rates.

5. Consistently low temperatures characterize both systems. Their effects on photo‐synthetic carbon uptake mirror shade‐adaptation. Division rates of marine phytoplankton may however be very much higher than predicted for ambient temperatures.

6. Vertical mixing is important in both ecosystems and influences the environment experienced by phytoplankton cells. This appears to have little effect on the average performance of phytoplankton in the strongly mixed surface water column of the Southern Ocean, where the mixed depth may exceed 100 m. This can be related partly to the shade‐adapted photosynthetic response. Euphotic depths range from 20 to 100 m.

7. Strong vertical mixing under ice‐free conditions in lakes may maximize photosynthetic efficiency, whilst distinct vertical stratification in permanently ice‐covered lakes gives rise to segregation of nutrient uptake and regeneration.

8. Physical removal of phytoplankton biomass by grazing is locally important in the Southern Ocean, in contrast to the estimated mean mesoscale impact of grazing. Vertical sedimentation losses appear important in the context of mixing depth and generation time, and may be modified by vertical circulation of water.

9. Loss of phytoplankton biomass from lakes during the ice‐free period is dominated by physical removal via the lake outflow. Grazing is generally unimportant, except where larvae of otherwise nektobenthic zooplankton hatch in synchrony with a phytoplankton maximum. Sedimentation is important under ice‐cover.
γ‐AMINOBUTYRIC ACID AND POSTGANGLIONIC SYMPATHETIC TRANSMISSION IN THE PULMONARY ARTERY OF THE RABBIT
Authors: STARKE K. , WEITZELL R.
Published: January 2008

The effect of γ‐aminobutyric acid (GABA) on postganglionic sympathetic neurotransmission was studied in strips of the rabbit pulmonary artery. The strips were preincubated with 3H‐noradrenaline and then superfused with 3H‐amine‐free medium. They were stimulated either electrically at 2 Hz, or by 60 mM potassium, or by 1 μM tyramine.

GABA (1 – 1000 μM) did not change the basal outflow of tritium, but decreased the electrically evoked overflow as well as the contractile response. GABA 1 μM decreased the evoked overflow by 12%, and GABA 1000 μM, by 42%. The effect of GABA was not changed by yohimbine, propranolol, cocaine, corticosterone, or indomethacin. It was not antagonized by picrotoxin or bicuculline methiodide. GABA 100 μM also slightly reduced the potassium‐evoked overflow of tritium but did not change the tyramineevoked overflow.

The results show that, in the pulmonary artery of the rabbit, GABA inhibits the release of noradrenaline. Its effect is independent of α‐ and β‐adrenoreceptors and is not mediated by prostaglandins. The effect may be due to activation of presynaptic receptors which appear to differ from conventional GABA receptors inasmuch as they are insensitive to blockade by either picrotoxin or bicuculline.
ADRENORECEPTOR‐MEDIATED RESPONSES IN THE ISOLATED PORTAL VEIN OF THE HYPOTHYROID RAT
Authors: LEE YOONG YAN , STORY MARGOT E. , ISHAC E. J. , PENNEFATHER JOCELYN N. , HANDBERG GWYNNETH M.
Published: January 2008

1 The effect of hypothyroidism, induced by methimazole, upon the respone of the isolated portal vein of the rat to adrenoreceptor agonists and antagonists, to angiotensin II and to papaverine has been investigated.

2 The positions and maxima of log dose‐response curves, to the vasoconstrictor agonists, noradrenaline and angiotensin II, and to the vasodilator agonists isoprenaline and papaverine, were unaffected by methimazole treatment.

3 The α‐adrenoreceptor antagonist phentolamine competitively inhibited the effects of noradrenaline to a similar extent in preparations from control and hypothyroid animals. The competitive antagonism of isoprenaline by the β‐adrenoreceptor antagonist propranolol was similarly unaffected by hypothyroidism.

4 These results taken together indicate that hypothyroidism is without significant effect upon either the properties of postjunctional α‐ β‐adrenoreceptors in the rat portal vein, or upon the reactivity of this blood vessel to the vasoactive agonists studied.
PHARMACOLOGY OF POSTSYNAPTIC α‐ADRENORECEPTORS IN THE MOUSE ANOCOCCYGEUS MUSCLE
Authors: GIBSON A. , YU O.
Published: January 2008

1 The α‐adrenoreceptor agonists noradrenaline (NA), methoxamine, phenylephrine, naphazoline, oxymetazoline, and xylazine produced contractions of the mouse anococcygeus muscle. All were full agonists.

2 Cocaine (2 μM) increased the pD2 values of NA and phenylephrine. 6‐hydroxydopamine pretreatment increased the pD2 values of NA, phenylephrine, and xylazine. After both procedures the order of potency of the agonists was oxymetazoline > naphazoline > NA > phenylephrine > methoxamine > xylazine.

3 The order of potency of antagonists against all six agonists was prazosin > phentolamine > yohimbine. However, from differences in the pA2 values and slopes of the Schild plots of the antagonists it was possible to distinguish three distinct groups of agonists: the phenylethylamines; the imidazolines; and the thiazine derivative xylazine.

4 The results suggest that the postsynaptic α‐adrenoreceptor of the mouse anococcygeus muscle may be broadly classified as α1. However, there may be at least three drug recognition sites on the receptor which interact with agonists of differing chemical structure.
ABSENCE OF A CHOLINERGIC COMPONENT IN NORADRENERGIC TRANSMISSION IN THE CERVICAL SYMPATHETIC NERVE OF THE RAT
Authors: MERCHANT S. J. , HUGHES I. E.
Published: January 2008

1 In rats anaesthetised with chloralose and pentobarbitone, frequency‐dependent tachycardia and contraction of the ipsilateral inferior eyelid occurred when the intact right cervical sympathetic nerve was stimulated.

2 After successive doses of 5, 12.5 and 30 μg.kg‐1 neostigmine sulphate (i.v.) a progressive reduction was seen in the tachycardias to low frequency stimulation (0.2 to 2 Hz) but either no effect, or an augmentation after 30 μg.kg‐1, was evident at higher frequencies (up to 20 Hz). Atropine sulphate (i.v., 100 μg.kg‐1) abolished the augmentatory effect of neostigmine on the high‐frequency responses and offset partially the depressant effect of neostigmine on the responses to 0.2 and 0.5 Hz. By contrast, contractions of the eyelid were unaltered by neostigmine and atropine.

3 Reserpinised rats (8 mg.kg‐1 i.p., 24 h earlier) were quite refractory to stimulation and remained so after neostigmine and atropine.

4 The effectiveness of neostigmine (enhancing responses) and atropine (inhibiting them) was demonstrated on endogenous acetylcholine (ACh) by measuring bradycardia to right efferent vagal stimulation, and on exogenous ACh by measuring inferior eyelid retraction in both reserpinised and control rats. These groups were equally sensitive to either ACh or noradrenaline and cocaine potentiated the tachycardia to nor‐adrenaline in both groups.

5 Propranolol reduced the tachycardia and phentolamine the eyelid contraction induced by sympathetic nerve stimulation.

6 The findings offer no support to a theory implying an obligatory cholinergic‐link in noradrenergic transmission.
REVIEW MODULATION OF NORADRENALINE RELEASE THROUGH ACTIVATION OF PRESYNAPTIC β‐ADRENORECEPTORS
Authors: MAJEWSKI H.
Published: January 2008

The Editor and publishers regret that owing to an unexpected delay at the printers the review articl above was published without incorporating the author's proof corrections. This has resulted in a regretabl high number of errors in the published paper. Below are listed corrections which may affect the understanding of the article and do not include all minor typographical errors. The Editor extends his apologies to the author and to the readership for this unfortunate occurrence.
INCREASED α2‐ADRENORECEPTOR MEDIATED VASCULAR CONTRACTION IN DIABETIC RATS
Authors: SCARBOROUGH N. L. , CARRIER G. O.
Published: January 2008

Contractile responses of aortic ring preparations from control and diabetic rats to nonselective (noradrenaline) and selective α1‐(phenylephrine) and α2‐ (clonidine) adrenoreceptor agonists were examined to determine the contribution of these receptor subtypes to the response.

Aortae from diabetic rats were more responsive to noradrenaline compared to age‐matched control rats. There was no difference between contractile responses of aortae from control and diabetic rats to phenylephrine, whereas clonidine‐induced contractions were enhanced in aortae from diabetic rats.

Dependence of clonidine‐induced contractions on extracellular calcium availability was determined. Each of the methods used indicated increased dependency of aortae from diabetic rats on extracellular calcium availability for clonidine‐induced contractile force generation.

These data indicate that the increased noradrenaline‐induced responsiveness of aortae from diabetic rats may be attributed to an increased α2‐adrenoreceptor component of the contractile response. It is also concluded that the α2‐adrenoreceptor mediated contraction is primarily dependent upon extracellular calcium. From this we suggest that the increased contractile responsiveness of aortae from diabetic rats to α2‐adrenoreceptor stimulating drugs may be related to an altered coupling mechanism between the α2‐adrenoreceptors and the calcium ion channels or due to a change in membrane permeability as a result of the disease process.
THE INHIBITORY EFFECT OF CLONIDINE ON THE OESTROGEN‐PRIMED RAT ISOLATED UTERUS
Authors: GOYAL R. K. , DAVE K. C. , VERMA S. C.
Published: January 2008

The investigation was undertaken to study the mechanism of the inhibitory effects of clonidine on the oestrogen‐primed rat isolated uterus.

Clonidine produced dose‐dependent relaxations of the rat isolated uterus which were competitively blocked by yohimbine but not by prazosin.

Metiamide, a specific H2‐histamine receptor antagonist, inhibited clonidine‐induced responses only at a high concentration (1.0 times 10‐6M).

Propranolol, a β‐adrenoreceptor antagonist produced competitive antagonism of the clonidine responses.

Like clonidine, noradrenaline also produced dose dependent relaxations of the rat isolated uterus. The responses to noradrenaline were not antagonized by either prazosin or yohimbine but were competitively antagonized by propranolol.

7 It is concluded that clonidine inhibits the uterus via an action on α2‐adrenoreceptors and possibly also to a lesser extent on H2‐histamine receptors, leading ultimately to release of noradrenaline from endogenous stores which causes relaxation by acting on β‐adrenoreceptors.