Alfred W. Bennett

Bio: Alfred W. Bennett is an academic researcher. The author has contributed to research in topics: Mimicry & Acclimatization. The author has an hindex of 8, co-authored 31 publications receiving 3644 citations.

The Origin of Species by means of Natural Selection; or the Preservation of Favoured Races in the Struggle for Life

Abstract: FEW are the writers, scientific or otherwise, who ca afford, in every successive edition of their works, to place side by side the passages which they have seen reason to alter, from a change of view or any other cause. And yet to this point we find especial attention called in each succeeding edition of Mr. Darwin's “Origin of Species.” And herein lies the true humility of the man of science. Science is often charged with being arrogant. But the true student of Nature cannot be otherwise than humble-minded. That man is unworthy of the name of a man of science who, whatever may be his special branch of study, has not materially altered his views on some important points within the last twelve years.* The means at our command for obtaining correct views of the laws which govern Nature are ever increasing, and if we only The Origin of Species by means of Natural Selection; or the Preservation of Favoured Races in the Struggle for Life. By Charles Darwin, M.A., F.R.S. Sixth edition, with additions and corrections. (London: J. Murray, 1872.)

The Genesis of Species

Abstract: IT is a remarkable illustration of the apparently fitful manner in which our knowledge of Nature increases, that the event which has probably been more fruitful than any other during the present century in inducing practical advances in the study of Natural History, was the promulgation of a pure theory, the publication, namely, by Mr. Darwin and Mr. Wallace, of the doctrine of the Origin of Species by means of Natural Selection. We say a pure theory, because the genesis of a new species is a phenomenon which never has yet, and probably never will, come consciously under the cognizance of man. We see forms of animal and vegetable life die out before our eves, but their birth is not within our ken. As Mr. Darwin has pointed out, even should a new species suddenly arise, we have no means of recognising it as such. As a matter of fact, new plants and animals are constantly being discovered in all parts of the globe. Even in our own small and well-searched island, the additions within the last twenty years of more or less conspicuous flowering plants to our native flora are not inconsiderable; but no naturalist suggests any other interpretation of this, than that either they have been overlooked before, have been recently introduced from other countries, or that the seeds have been buried for ages in the soil. None the less, however, does it seem possible, or even probable, that we may eventually arrive at a correct solution of the problem by a rigorous induction from known facts.

The Flora of Canada

Abstract: THE review by Mr. J. G. Baker in your last number (p. 242) of the second part of Prof. Macoun's “Catalogue of Canadian Plants” prompts me to send you a few notes on some of the features of the flora of Canada, which I had an unusual opportunity of observing last autumn under the guidance of Prof. Macoun in the neighbourhood of Ottawa, and again in the magnificent railway trip given to members of the British Association by the Canadian Pacific Railway Company from Lake Superior to Kicking-Horse Pass in the Rocky Mountains.

On the Fertilisation of Winter-Flowering Plants

Abstract: THAT the stamens are the male organ of the flower, forming unitedly what the older writers called the “andrœcium,” is a fact familiar not only to the scientific man, but to the ordinary observer. The earlier botanists formed the natural conclusion that the stamens and pistil in a flower are intended mutually to play the part of male and female organs to one another. Sprengel was the first to point out, about the year 1790, that in many plants the arrangement of the organs is such, that this mutual interchange of offices in the same flower is impossible; and more recently, Hildebrand in Germany, and Darwin in England, have investigated the very important part played by insects in the fertilisation of the pistil of one individual by the stamens of another individual of the same species. It is now generally admitted by botanists that cross-fertilisation is the rule rather than the exception. The various contrivances for ensuring it, to which Mr. Darwin has especially called the attention of botanists, are most beautiful and interesting; and the field thus opened out is one which, from its extent, importance, and interest, will amply repay the investigation of future observers. For this cross-fertilisation to take place, however, some foreign agency like that of insects is evidently necessary, for conveying the pollen from one flower to another. The question naturally occurs, How then is fertilisation accomplished in those plants which flower habitually in the winter, when the number of insects that can assist in it is at all events very small? I venture to offer the following notes as a sequel to Mr. Darwin's observations, and as illustrating a point which has not been elucidated by any investigations that have yet been recorded. I do not here refer to those flowers of which, in mild seasons, stray half-starved specimens may be found in December or January, and of which we are favoured with lists every year in the corners of newspapers, as evidence of “the extraordinary mildness of the season.” I wish to call attention exclusively to those plants, of which we have a few in this country, whose normal time of flowering is almost the depth of winter, like the hazel-nut Corylus avellana, the butcher's broom Ruscus aculeatus, and the gorse Ulex europœus; and to that more numerous class which flower and fructify all through the year, almost regardless of season or temperature; among which may be mentioned the white and red dead-nettles Lamium album and purpureum, the Veronica Buxbaumii, the daisy, dandelion, and groundsel, the common spurge Euphorbia peplus, the shepherd's purse, and some others.

Leonardo Da Vinci as a Botanist

Abstract: FEW men have better earned the title of universal genius than Da Vinci. An ardent disciple of Nature, disdaining mere superficial knowledge, he went to the root of whatever he took up, and attained an intimate acquaintance especially with everything that bore on his beloved art of painting. And this art was understood by him in its widest sense. Not content with representing the mere outward appearance of Nature or of the human form, he considered it a part of his business as a painter to investigate the laws which produce those appearances or which govern that form in its healthy state. To the long list of his acquirements given in the catalogue of the Louvre collection, as painter, sculptor, architect, engineer, physicist, writer, and musician, may now be added that of botanist. In the first number of a new botanical journal, Nuovo Giornale Botanico Italiano, published at Florence, Sig. G. Uzielli has given some interesting extracts from a work by Da Vinci, from which he would appear to have anticipated the discovery of certain botanical laws generally attributed to writers of a later age. These extracts are taken from a section of his great treatise on painting, entitled “On Trees and Vegetation,” which, however, is found only in one edition of that work, the Roman. The following are the points on which the originality of his observations deserves especial mention.

Punctuated equilibria; the tempo and mode of evolution reconsidered

Abstract: We believe that punctuational change dominates the history of life: evolution is concentrated in very rapid events of speciation (geologically instantaneous, even if tolerably continuous in ecological time). Most species, during their geological history, either do not change in any appreciable way, or else they fluctuate mildly in morphology, with no apparent direction. Phyletic gradualism is very rare and too slow, in any case, to produce the major events of evolution. Evolutionary trends are not the product of slow, directional transformation within lineages; they represent the differential success of certain species within a clade—speciation may be random with respect to the direction of a trend (Wright's rule).As an a priori bias, phyletic gradualism has precluded any fair assessment of evolutionary tempos and modes. It could not be refuted by empirical catalogues constructed in its light because it excluded contrary information as the artificial result of an imperfect fossil record. With the model of punctuated equilibria, an unbiased distribution of evolutionary tempos can be established by treating stasis as data and by recording the pattern of change for all species in an assemblage. This distribution of tempos can lead to strong inferences about modes. If, as we predict, the punctuational tempo is prevalent, then speciation—not phyletic evolution—must be the dominant mode of evolution.We argue that virtually none of the examples brought forward to refute our model can stand as support for phyletic gradualism; many are so weak and ambiguous that they only reflect the persistent bias for gradualism still deeply embedded in paleontological thought. Of the few stronger cases, we concentrate on Gingerich's data for Hyopsodus and argue that it provides an excellent example of species selection under our model. We then review the data of several studies that have supported our model since we published it five years ago. The record of human evolution seems to provide a particularly good example: no gradualism has been detected within any hominid taxon, and many are long-ranging; the trend to larger brains arises from differential success of essentially static taxa. The data of molecular genetics support our assumption that large genetic changes often accompany the process of speciation.Phyletic gradualism was an a priori assertion from the start—it was never “seen” in the rocks; it expressed the cultural and political biases of 19th century liberalism. Huxley advised Darwin to eschew it as an “unnecessary difficulty.” We think that it has now become an empirical fallacy. A punctuational view of change may have wide validity at all levels of evolutionary processes. At the very least, it deserves consideration as an alternate way of interpreting the history of life.

The linnean society of london

Abstract: This issue contains the concluding instalment on Richard Owen and the Dinosauria. One hundred and fifty years on, Owen would view with incredulity our present day obsession with this group of extinct monsters. Like Cuvier, he believed these ‘fearfully great lizards’ to be no more than glorified crocodiles, although he later demonstrated that Megalosaurus in its method of tooth succession was closer to the mammalian class than to crocodiles or lacertians. Moreover, since he believed that mammals and birds were related (a view

Conceptual Synthesis in Community Ecology

Abstract: Community ecology is often perceived as a mess, given the seemingly vast number of processes that can underlie the many patterns of interest, and the apparent uniqueness of each study system. However, at the most general level, patterns in the composition and diversity of speciesthe subject matter of community ecologyare influenced by only four classes of process: selection, drift, speciation, and dispersal. Selection represents deterministic fitness differences among species, drift represents stochastic changes in species abundance, speciation creates new species, and dispersal is the movement of organisms across space. All theoretical and conceptual models in community ecology can be understood with respect to their emphasis on these four processes. Empirical evidence exists for all of these processes and many of their interactions, with a predominance of studies on selection. Organizing the material of community ecology according to this framework can clarify the essential similarities and dif...

An analysis of particle swarm optimizers

Abstract: Many scientific, engineering and economic problems involve the optimisation of a set of parameters. These problems include examples like minimising the losses in a power grid by finding the optimal configuration of the components, or training a neural network to recognise images of people's faces. Numerous optimisation algorithms have been proposed to solve these problems, with varying degrees of success. The Particle Swarm Optimiser (PSO) is a relatively new technique that has been empirically shown to perform well on many of these optimisation problems. This thesis presents a theoretical model that can be used to describe the long-term behaviour of the algorithm. An enhanced version of the Particle Swarm Optimiser is constructed and shown to have guaranteed convergence on local minima. This algorithm is extended further, resulting in an algorithm with guaranteed convergence on global minima. A model for constructing cooperative PSO algorithms is developed, resulting in the introduction of two new PSO-based algorithms. Empirical results are presented to support the theoretical properties predicted by the various models, using synthetic benchmark functions to investigate specific properties. The various PSO-based algorithms are then applied to the task of training neural networks, corroborating the results obtained on the synthetic benchmark functions.