Lower Stages Of Development Research Articles

Analysis of competitive interactions between the limpets Patella depressa Pennant and Patella vulgata L. on the northern coast of Portugal

Inter- and intraspecific competitive interactions among the species Patella depressa Pennant and P. vulgata L. were analysed on the northern coast of Portugal, where both species co-occur in similar proportions. Increased (×2, ×4), normal and decreased (×1/2 intraspecific only) densities of limpets were used to test the effects of competition on the growth and mortality of the limpets, and competitive interactions between the different species. Fenced plots of 25×25 cm enclosing marked limpets at various densities were set up at a mid tidal level on the shore. Twelve treatments with three replicates of different combinations of densities and species were established. Mortality was recorded every 15 days and length was measured monthly during the 5 months of the experiment. At the end of the experiment, limpets were collected for biometry, sex determination and gonad staging. Both species of grazing molluscs showed increased mortality and reduced size and weight in increased density treatments. Limpets in decreased density treatments showed lower mortality and higher size. There were no significant differences between the effect of P. vulgata on P. depressa and the effect of P. depressa on P. vulgata on mortality and length. There were, however, decreases in weight due to intraspecific effects for both species. For P. vulgata, interspecific effects were much less than intraspecific effects and for P. depressa, the interspecific effects depended on density. The analysis of the gonad stage at the end of the experiment showed that the lower stages of development were most prevalent at increased densities and the occurrence of neuter individuals only in increased densities single species plots corroborated the evidence of a stronger intraspecific interaction. The availability of food was indirectly assessed by determination of chlorophyll concentration with spectrophotometric analysis of rock chips. Microalgal food assessment in this experiment, however, did not show any clear trends. The results were compared with previous studies of competition in grazing molluscs and discussed in relation to the limits of distribution of P. vulgata on the Portuguese coast.

The Distribution of Human Capital and Economic Growth

This paper analyzes the interaction between the distribution of human capital, technological progress, and economic growth. It argues that the composition of human capital is an important factor in the determination of the pattern of economic development. The study demonstrates that the evolutionary pattern of the human capital distribution, the income distribution, and economic growth are determined simultaneously by the interplay between a local home environment externality and a global technological externality. In early stages of development the local home environment externality is the dominating factor and hence the distribution of income becomes polarized; whereas in mature stages of development the global technological externality dominates and the distribution of income ultimately contracts. Polarization, in early stages of development may be a necessary ingredient for future economic growth. An economy that prematurely implements a policy designed to enhance equality may be trapped at a low stage of development. An underdeveloped economy, which values equality as well as prosperity, may confront a trade-off between equality in the short-run followed by equality and stagnation in the long-run, and inequality in the short-run followed by equality and prosperity in the long run.

Start-up costs and pecuniary externalities as barriers to economic development

We use a dynamic monopolistic competition model to show that an economy that inherits a small range of specialized inputs can be trapped into a lower stage of development. The limited availability of specialized inputs forces the final goods producers to use a labor intensive technology, which in turn implies a small inducement to introduce new intermediate inputs. The start-up costs, which make the intermediate inputs producers subject to dynamic increasing returns, and pecuniary externalities that result from the factor substitution in the final goods sector, play essential roles in the model.

New oilseed crops on the horizon

Fats and oils for food uses are now plentiful on a worldwide basis. Tallow, lard and fish oils, as well as vegetable oils, such as those derived from soybean, sunflower, palm, rapeseed, peanut and cottonseed, are often overproduced. Although many of these products are also used for industrial chemicals, they often are not of the most favorable composition for nonfood applications. A search for new oil-seed crops with more advantageous oil composition has led to the development of excellent candidates that are now close to commercial acceptance. Among them areCrambe, Limnanthes, Vernonia, Sapium andSimmondsia. Other crops are at a much lower stage of development but also have excellent potential. They includeCuphea, Foeniculum, Stokesia, Lesquerella andLunaria. In this age of searching for renewable resources to replace petrochemicals and imported strategic materials, a well-organized research and development program on new oilseed crops could soon result in American self-sufficiency for industrial oils and fatty acids. Fats and oils for food uses are now plentiful on a worldwide basis. Tallow, lard and fish oils, as well as vegetable oils, such as those derived from soybean, sunflower, palm, rapeseed, peanut and cottonseed, are often overproduced. Although many of these products are also used for industrial chemicals, they often are not of the most favorable composition for nonfood applications. A search for new oilseed crops with more advantageous oil composition has led to the development of excellent candidates that are now close to commercial acceptance. Among them areCrambe, Limnanthes, Vernonia, Sapium andSimmondsia. Other crops are at a much lower stage of development but also have excellent potential. They includeCuphea, Foeniculum, Stokesia, Lesquerella andLunaria. In this age of searching for renewable resources to replace petrochemicals and imported strategic materials, a well-organized research and development program on new oilseed crops could soon result in American self-sufficiency for industrial oils and fatty acids.

Electron microscopy of polyps of the colon, II. Inclusion bodies of Leuchtenberger

The electron-microscopic characteristics of the LEUCHTENBERGER'S inclusion bodies were studied in adenomatous, papillary and adeno-papillary polyps of the colon. According to them, formation of intracellular inclusions is due to focal cytoplasmic degradation, and that of intercellular inclusions to the herniation of the cytoplasmic part of epithelial cells. The formation of inclusions is believed to be connected with the low stage of development of the plasma membrane of rapidly proliferating undifferentiated colonic epithelial cells. During malignant transformation of polyps, the frequently occurring inclusions are considered an important morphological sign.

Brief Reports: The Effects of Perceptual Transformation Experiences and Numerical Operational Experiences on Numerical Correspondence and Equivalence

Piaget's theoretical and empirical accounts of young children's development of an understanding of numerical correspondence and equivalence has stimulated extensive research and analysis. A critical examination of a wide variety of training reports indicates that in a majority of the successful investigations, subjects have possessed some aspects of the conservation response (i.e., the ability to establish one-to-one correspondence or the ability to conserve on one but not two items) prior to their inclusion in the study. In the unsuccessful studies, subjects have been generally classified as “nonconservers” without specification of developmental status. This non-specific classification suggests that children at lower stages of development (i.e., unable to establish one-to-one correspondence) were included in the sample. A second interesting observation is that although training sessions provided experiences for learning to (a) establish one-to-one correspondence, (b) recognize the eq ui valence of matched sets, and (c) maintain equi valence during perceptual transformations, assessment of the effectiveness of training has been only in terms of the maintenance of equivalence during perceptual transformations. No examination has been made of the effectiveness of training approaches in facilitating learning of the other two aspects, which are viewed as conservation subskills and necessary conditions for conservation. Nor have there been any previous studies to assess the differential effectiveness of training for preconservation children at various stages of development.

La développement des pêches régionales en Afrique occidentale

The fishing grounds off the coast of West Africa are among the most productive in the world. Catches in the area in 1970 were in excess of 2 million tons, an increase of about 100% over 1960s catch. Of this only a third was caught by canoes and fleets bordering the region, the rest by an increasing number of large vessels from countries outside Africa.Fishing is still a subsistence activity in all coastal districts and locally based modern vessels are few. Although fish processing industries have been developed in several countries of the region they often remain at a low level of production because of insufficient supply of raw material.Fish consumption in the area — marine and fresh water fish — is estimated at about 1 million tons for a population of 150 million, including the landlocked countries of the Gulf of Guinea. Although imports supply 20% of the fish consumed in the area, there is a deficit of half a million tons. This deficit could well reach 1 million tons in the course of the next decade under the combined pressure of population growth and rising incomes.The uneven distribution of the producing areas and the general demand for fish suggests a potential for a large expansion of interregional trade. The need for the coastal states to develop their fisheries and fishery industries is obvious.The rapid increase of the catch by foreign fleets is causing a number of West African countries to extend their territorial waters beyond the 12-mile limit. This, in turn, is inducing foreign concerns to seek cooperation with the coastal countries. A greater participation of these countries in the exploitation of the resources of their continental shelf should result from the new strategy.In view of the low stage of development in the area an integrated policy for development is needed. This would cover small craft and large vessels, fish processing and marketing, resources assessment and monitoring, aquaculture and training, at all levels in fisheries. Such a strategy is outlined in the paper.

Half a Century on the Path to Communism

Marxism is a teleological creed. Even though the founding fathers of this ideology did not wish to resemble the Utopian socialists who had attempted to describe in some detail the eventual good society, Marx and Engels clearly laid down the belief that history must move toward an appointed goal: a classless society in which mankind can flourish as never before. To this day the orthodox Marxists accept this thesis. Indeed, it is partly the question of accepting or rejecting it that separated the revisionists such as Eduard Bernstein from the orthodox about seventy years ago and continues to separate social democrats from Communists. To the orthodox Communist, the October Revolution was the crucial and most dramatic step on the road to the ultimate society, but not the last. Following Marx's Critique of the Gotha Program, inspired by the German socialists' draft of 1875, Communists believe that society passes from capitalism into a lower stage of development, now generally called socialism, and only later into the ultimate stage that is now called communism.1 It is only in this latter stage that society may inscribe on its banners: From each according to his ability, to each according to his needs!

On the Nerve Supply of the Dorsum Linguae and the Facies Inferior Linguae in Newborn Dog

The filiform papillae in the dorsum linguae of newborn dog are small-sized and of short cylindrical form; they are still in a low stage of development and consequently the number of the sensory fibres coming into their stocks is also very small. These fibres form undranched and simple branched terminations beneath the epithelium. The stem fibres are usually medium-sized, but sometimes thick stem fibres are also present and send out terminal fibres which show conspicuous change in size and some windings in their courses. The above findings are not much different from what has been reported on the same papillae of the adult dog. Neither intraepithelial fibres nor corpuscular terminations have been found in the filiform papillae.The fungiform papillae were much larger than the filiform papillae and their epithelium often contains taste-buds. In most of these papillae, a single nerve bundle runs through the basis into the stock and sends out nerve fibres radially toward the epithelium. The nerve fibres consist of fine vegetative and thick sensory fibres, of which the former end in STOHR's terminal reticula, but the latter end in unbranched and simple branched terminations beneath the epithelium. These sensory terminations are somewhat more complex than those in the filiform papillae above. The fungiform papillae contain some intraepithelial fibres of simplest unbranched type, but bifurcated intraepithelial terminations are not rare either. The sensory nerve supply to the taste-buds in these papillae is very poor indeed, some of the taste-buds being utterly devoid of any sensory fibre. No corpuscular termination was found in these papillae either.The foliate papillae on the tongue of the newborn dog were rather typically formed and taste-buds were abundant in the epithelium not only on the sides of the surrounding furrow but also on the side facing directly the oral cavity.The circumvallate papillae are small both in size and in number. Taste-buds are contained in the epithelium facing the oral cavity and in a smaller and variable number in the epithelium lining the sides of the surrounding furrow. The epithelium of the oral-cavity side was not yet found anywhere depressed, as observed in such papillae of the adult dog.Basal plexus containing REMAK's hemiganglion cells is formed in the basis of the foliate and the circumvallate papillae. This plexus consists of a larger number of fine vegetative fibres and somewhat fewer thick sensory fibres. The former end in very well-developed terminal reticula in the papillary stocks, while the latter fibres, much more numerous than in the fungiform papillae, spread out radially toward the epithelium and end beneath it. The sensory terminations are mostly of simple branched type, complex ones being as yet unformed. These sensory terminations come into very intimate relation with the vegetative fibres and terminal reticula. They are most often formed just beneath the taste-buds and their terminal fibres often run into the epithelium to end in intra- and extra-gemmal fibres. The terminal fibres frequently show marked change in size and within the epithelium, often end bluntly or in small knobs.The facies inferior linguae of the newborn dog is generally surfaced by a thin smooth non-cornified stratified flat epithelium. The propria here is also rather thin, and the papillae growing out of the propria into the epithelium are usually very ill developed, but somewhat larger papillae are found near the median line. A few longitudinal mucous folds are formed on the facies inferior.The facies inferior contains only very ill-developed proprial plexus, and consequently, the sensory fibres therein are also very scanty. The sensory terminations here too are of unbranched and simple branched types only

Histological study on innervation of pars mucosa of vestibulum nasi in human embryo.

The nasal vestibule is already in good development in the latter stage of the embryonic life, and is divisible, as in adult, primarily into the cutaneous part overgrown with hairs and the mucous part succeeding it on the inner side. In the latter part, however, the distinction of the three parts of the corneal, the noncorneal and the transitional, distinguished by the nature of the epithelium and the formation of papillae, is not yet sufficiently clear. In 6th month embryos, the corneal part is nearly complete, but the non-corneal and transitional parts are both surfaced with thick stratified columnar epithelium, so that their boundary is not clear-cut. In 10th month embryos, the surface of the epithelium in the frontal half of the non-corneal part has changed to stratified flat epithelium, but the rear half remains as yet surfaced with stratified columnar epithelium, and the boundary between the non-corneal and the transitional part remains yet undefined. Papillae are formed in considerable development in the cor-neal part, but almost none in the non-corneal part. The end apparatus of the vegetative nerve fibres is completed as Stohr's terminal-reticulum, and stands in tactile control against the nasal glands, the blood vessels, in particular, the capillaries. There are comparatively few sensory nerve fibres supplying the mucous membrane of the nasal vestibule. Most of the fibres run into the lamina propria and end beneath the epithelium and some run further into the epithelium to end as intraepithelialfibres. As sensory fibres penetrate preferentially into papillae, the corneal part having papillae is provided with better developed sensory fibres than the non-corneal part without papillae. That is, the sensory fibres in the corneal part are generally thick and end in somewhat differentiated terminations, while those.in the non-corneal part are mostly minute and end in simple ones. But these sensory terminations are as yet in much lower stage of development in comparison with those in adult, mostly being represented by the simple unbranched endings, especially in 6th month embryos. The second type of sensory terminations is represented by the simple branched terminations composed of 2-3 rami which are found rather often in the 10th month embryos. The third type of sensory nerve endings is corpuscular in form, but such terminal bodies are as yet not formed in the latter stage of embryonic life. But the terminations showing a very simple glomerular arrangement of sensory fibres, presumably precursors of such bodies, are in some cases found in the major papillae in the corneal part. The fourth type of sensory endings, the intraepithelial fibres, has been proved to exist in the latter embryonic stage, but their infantile form and small number seem to indicate their full-fledged development to be post-poned till after birth. Namely, in 6th month embryo, the intraepithelial fibres are very few in number, are minutely thin and end unbranched after running a short course. In 10th month embryos, these fibres appear with greater incidence, and their terminal mode becomes more complex. For example, in the non-corneal part, there are seen often also bifurcated terminations, and in the corneal part, also branched intraepithelial fibres of medium size. Besides, in both the above parts, many sensory terminal fibres are found touching the basal layer of the epithelium or slightly penetrating it. These fibres probably develop into intraepithelial fibres in post-natal life. Into the strongly developed papillae in the frontal area of the corneal part penetrate stout sensory never fibres to end there sharply or bluntly, but unlike those in adult, none of them has ever been found to run further up into the epithelium, to end as the peculiar thick and short intraepithelial fibre.

Sensory innervation of urogenital organs of fourth month female embryo.

The innervation of urogenital organs in a fourth month female em-bryo may be cotlined as follows. In the distal part of the ureter, unbranched, and on rarer occasions, simple branched sensory terminations may be found in the propria. How-ever, intraepithelial fibres and glomerular terminations are not yet formed. In the bladder, only unbranched and simple branched terminations are observed in formation. In rare cases, intraepithelial fibres were proved to exist. In the urethra, sensory fibres run into the propria from the outside wall. Their terminations are also unbranched and simple branched ter-minations, and no genital nerve bodies nor intraepithelial fibres were ob-served. In the propria of the uterus, a small number of unbranched termina-tions are found. This fact seems to indicate the presence of sensory ter-minations in adult human uterus. In the vaginal wall, scarcely any sensory fibres are verified. Only near the outer orifice, a small number of unbranched terminations were observed. In the vestibulum vaginae, the number of sensory fibres is much larger, the terminations being mostly of unbranched type. In the labium minus, the number increases further, unbranched and simple branched terminations being in evidence, but no complex branched terminations nor genital nerve bodies are found. As sensory terminations in the clitoris, Pacinian bodies may be men-tioned first. Their number is yet very small, and their formation is found around the tunica albuginea of the corpus cavernosum clitoridis, and on rare occasions, in the corpus cavernosum glandis. It is interesting to note that Pacinian bodies are formed in places in the fascial formation around the pubis, unrelated with the clitoris. These Pacinian bodies are naturally in the inchoate stage of development by fourth month embryo. In the clitoris, no genital nerve bodies are found, not even a trace of them. Sensory terminations other than the Pacinian bodies are repre-sented by unbranched and extremely simple branched terminations, which are formed in the tunica propria glandis and the connective tissue in the praeputium in particular. In the terminal parts of the branches of n. dorsalis clitoridis, frequently very thick sensory fibres are seen branching out in several branches, which seems to show the fact that one thick nerve fibre may run out in a number of nerve terminations, or probably in many genital nerve bodies. In conclusion, I may mention the interesting fact that intraepithelial fibres are already seen in formation in the common epithelium between the inner lamella of the praeputium and the glans clitoridis, although, maybe, in a much lower stage of development than in a seventh month embryo (Seto), and that they are clearly distinguished into two separate types (Seto) in formation.