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A medical genetics clinic is a unique and complex environment in which care requires a combination of medical knowledge, social intelligence, and emotional sensitivity. We offer a few pearls from our medical genetics clinic that we hope will help the pediatric or general dermatologist when caring for patients with known or suspected genetic disorders. This paper addresses five main topics: When is it more than just atopic dermatitis? How should the clinician approach blistering in the newborn period? What is mosaicism? When is genetic testing useful? Where can clinician, patients, and families turn for available resources?

The geophysical inversion with combining prior information is very important for resource exploration and studies of the Earth’s internal structure. Guided fuzzy C-means clustering inversion (FCM) is normally applied for the Tikhonov regularized inversion, but has the shortcoming of uniform model parameter shrinkage, leading to inaccuracy. In this paper, an improved guided fuzzy clustering algorithm is proposed by adding a fuzzy entropy term to the original guided FCM. This method not only enforces the discrete values to a high degree of approximation by guiding the recovered model to cluster tightly around the known petrophysical property values, but also calculates the distributed characteristics of the model parameter set. Based on this method, the shortcoming of uniform shrinkage of the original guided FCM clustering algorithm is improved, and more accurate inversion results are obtained, making the FCM method more efficient and broadly applicable. Furthermore, a new parameter search algorithm is proposed to accelerate the search speed. The results recovered by using this method with three kinds of theoretical gravity anomaly data show more accurate density anomalies compared with the results generated from the original guided FCM clustering inversion and greater efficiency in the parametric search process when using the new parameter search algorithm. The improved FCM clustering algorithm could enable more extensive and efficient use of gravity inversion.

Background The health system in South Sudan faces extreme domestic resource constraints, low capacity, and protracted humanitarian crises. Supportive supervision is believed to improve the quality of health care and service delivery by compensating for flaws in health workforce management. This study aimed to explore the current supervision practices in South Sudan and identify areas for quality improvement. Methods The study employed qualitative approaches to collect and analyse data from six purposefully selected counties. Data were collected from 194 participants using semi-structured interviews (43 health managers) and focus group discussions (151 health workers). Thematic content analysis was used to yield an in-depth understanding of the supervision practices in the health sector. Results The study found that integrated supportive supervision and monitoring visits were the main approaches used for health services supervision in South Sudan. Supportive supervision focused more on health system administration and less on clinical matters. Although fragmented, supportive supervision was carried out quarterly, while monitoring visits were either conducted monthly or ad hoc. Prioritization for supportive supervision was mainly data driven. Paper-based checklists were the most commonly used supervision tools. Many supervisors had no formal training on supportive supervision and only learned on the job. The health workers received on-site verbal feedback and, most times, on-the-job training sessions through coaching and mentorship. Action plans developed during supervision were inadequately followed up due to insufficient funding. Insecurity, poor road networks, lack of competent health managers, poor coordination, and lack of adequate means of transport were some of the challenges experienced during supervision. The presumed outcomes of supportive supervision were improvements in human resource management, drug management, health data reporting, teamwork, and staff respect for one another. Conclusion Supportive supervision remains a daunting task in the South Sudan health sector due to a combination of external and health system factors. Our study findings suggest that strengthening the processes and providing inputs for supervision should be prioritized if quality improvement is to be attained. This necessitates stronger stewardship from the Ministry of Health, integration of different supervision practices, investment in the capacity of the health workforce, and health infrastructure development.

In heterogeneous wireless networks, random packet loss and high latency lead to conventional TCP variants performing unsatisfactorily in the case of competing communications. Especially on high-latency wireless links, conventional TCP variants are unable to estimate congestion degrees accurately for fine-grained congestion control because of the effects of random packet loss and delay oscillations. This paper proposes a TCP variant at the sender side to identify congestion degrees, namely TCP-WBQ, which quickly responses to the real congestion and effectively shields against random packet loss and oscillations of latency time. The proposed algorithm of congestion control firstly constructs a backlog-queue model based on the dynamics of the congestion window, and deduces the two bounds of the model which delimit oscillations of the backlog queue for non-congestion and random packet loss respectively. TCP-WBQ detects congestion degrees more accurately and thus implements the corresponding schemes of adjusting the congestion window, maintaining a tradeoff between high throughputs and congestion avoidance. The comprehensive simulations show that TCP-WBQ works efficiently in bandwidth utilization with single and multiple bottleneck scenarios, and achieves high performance and competitive fairness in heterogeneous wireless networks.

This paper provides a new solution to the epistemic paradox of ‘belief-instability’, a problem of rational choice which has recently received considerable attention (versions of the problem have been discussed by — among others — Tyler Burge, Earl Conee, and Roy Sorensen). The problem involves an ideally rational agent who has good reason to believe the truth of something of the form

Wide field application of curve number (CN) methodology in design flood estimation and forecasting studies is a well-accepted reality. The parameter CN is often regarded as a constant, but it is in fact a random variable, for it relies on a number of factors governing the process of rainfall-runoff. This paper suggests an alternative procedure to estimate design runoff (Q) using design storm (P) and design curve number (CN) values. To this end, design CN values for different durations and return periods have been derived from 25 years of daily annual maximum P-Q data of 10 Indian catchments. When compared, the computed design Q from design CN values was either very close to or slightly greater than the observed Q. The performance is also evaluated using coefficient of determination (R2), percentage of bias (PBIAS), and normalized Nash-Sutcliffe efficiency (NNSE). The magnitude of design CN is found to decrease for longer durations and smaller return periods, and vice versa, and such a behavior invoked the development of an empirical relation for estimation of design CN from given return period and duration for gauged as well as ungauged watersheds. The statistical analysis revealed the general extreme value (GEV) to fit best the P-CN series, whereas multiple probability distributions, viz., GEV, Gumbel max, log Pearson 3, and Gen Pareto fitted best the Q series. The 50-year, 100-year, and 200-year runoff estimated from the P-CN series exceeded only marginally those derived from the conventional Q series approach.

The development of a DNA microfluidic device with a high speed, low power, and low reagent volume is very critical for real-time genotyping and diagnosis in point-of-care applications. This paper reports a polymer-based thermal cycler for a handheld and battery-powered polymerase chain reaction (PCR) system using a polyimide (PI) film-based micro-fabricated heater module and polymer film microfluidic chambers of 10 μL, with a handheld and low power consumption, compared to state of the art. It took 21 min for 40 thermal cycling for DNA amplification and a maximum power consumption of 0.6 W. The microheater on PI film substrate fabricated and real-time quantification of deoxyribonucleic acid (DNA) using the heater in hand-held sizes experimentally shown here. The device would be applicable for on-site molecular diagnostics.

Eradication of aquatic weeds has been found to involve huge expenditure and is seldom practised. The present paper describes the use of dried Salvinia material in the manufacture of paper. The sheets have been checked for burst, breaking length, folding capacity, etc. Sheets prepared by a mixture of dried Salvinia and rice straw can be used safely as packing material in addition to several other uses.

Modeling rock breakage by explosions is essential for the proper choice of the parameters of drilling and blasting operations. In terms of the kinetic strength theory [i, 2], the present paper suggests a method for evaluating the characteristics of the zones of breakage and heightened microfissuring formed in hard rock masses by explosive stress waves from a blast hole charge. The method is used to study how the position of the detonator in the charge affects the result of the charge action on the rock mass.

Additive manufacturing (AM) systems present tremendous advantages over the traditional manufacturing systems, particularly for realizing complex shapes and producing custom parts. These advantages, and the rapid growth in the availability of AM systems, have led to a widespread increase in the use of AM. Unfortunately, general design for additive manufacturing (DfAM) tools that predict the engineering performance of AM parts are largely unavailable, and this has forced engineers to rely on engineering judgment and/or data from physical experiments. The data sets reported in the literature that quantify the performance of the existing AM systems provide much needed insight, but the data produced by experiments conducted on specific AM systems are necessarily of limited applicability. Given the large number of AM systems currently in use today, a potentially vast amount of data are needed to fully understand them all, and new AM systems and materials are being developed almost daily. To mitigate this need for an ever-increasing amount of data, this paper proposes the use of an approximation-assisted multi-objective optimization technique to quantify the performance of an AM system for specific design application in a targeted fashion. This general approach uses a limited number of physical experiments to answer a specific DfAM question of interest, and the results can then be used to design functional parts without the need for additional data. The implementation of the proposed approach is demonstrated with a material extrusion case study.

Traveling salesman problem with time windows (TSPTW) is a well-known problem in logistics management. It seeks to find a minimum cost tour among customers while all customers are visited at their time windows. To better reflect the real situations of logistics management, this paper concentrates on customers’ satisfaction aspect of TSPTW, extends the basic mathematical modeling of the problem to fuzzy traveling salesman problem with time windows (FTSPTW), and presents an ant colony system algorithm to solve the problem. One advantage of this new modeling is its flexibility which enables us to optimize the delivery process in the network of customers with different satisfaction patterns and different priorities. The other advantage is that by the use of fuzzy time windows, not only customers’ preference for tolerable interval of time for service but also desirable time for service can be considered. Numerical results for a well-known benchmark problem and a real case study both confirm that optimization of the customers’ satisfaction is completely different from traditionally minimizing the total traveling time as well as the proposed algorithm which considers that customers’ favorites is completely superior to the algorithm that only pays attention to minimizing total travel time. These results provide an opportunity for future comparisons of different solution methods for the FTSPTW.

In this paper are explored the ethical implications of the answers to three questions: Whether or not a diseased state is discrete; the criteria by which that question is answered; and how the diseased state is to be identified. Examples are given showing that some states appear to be clearly discrete, and others equally clearly not discrete. The nature of the pertinent evidence will be affected accordingly. It is shown that a slavish and inappropriate concern with categories leads to anomalous ethics. Finally, it is suggested that many of these problems may be avoided by centering the ethics of medicine on optimizing the welfare of the patient rather than by thinking in terms of categorical disease.

This paper provides an extensive review of the literature on spatial transferability of travel forecasting models. From the review, a synthesis is prepared on: (1) the theoretical and practical considerations related to model transferability, (2) the approaches and metrics used to assess model transferability, (3) the methods used to transfer models, and (4) the empirical evidence on model transferability. Building on this review, an agenda is developed for future research focusing on how best to assess transferability and to enhance model transferability. Potentially fruitful avenues for further research are identified throughout the paper. Further, a detailed discussion is presented on the various aspects that need to be considered while assessing the transferability of activity-based travel demand model systems.

The effects of the aspect ratio on unsteady solutions through the curved duct flow are studied numerically by a spectral based computational procedure with a temperature gradient between the vertical sidewalls for the Grashof number 100 ⩽ Gr ⩽ 2 000. The outer wall of the duct is heated while the inner wall is cooled and the top and bottom walls are adiabatic. In this paper, unsteady solutions are calculated by the time history analysis of the Nusselt number for the Dean numbers Dn = 100 and Dn = 500 and the aspect ratios 1 ⩽ γ ⩽ 3. Water is taken as a working fluid (Pr = 7.0). It is found that at Dn = 100, there appears a steady-state solution for small or large Gr. For moderate Gr, however, the steady-state solution turns into the periodic solution if γ is increased. For Dn = 500, on the other hand, it is analyzed that the steady-state solution turns into the chaotic solution for small and large Gr for any γ lying in the range. For moderate Gr at Dn = 500, however, the steady-state flow turns into the chaotic flow through the periodic oscillating flow if the aspect ratio is increased.

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This paper depicts a case study of an organizational strategy for the promotion of ethical practice when introducing a new, high-risk, ethically-charged medical practice like Medical Assistance in Dying (MAiD). We describe the development of an interprofessional program that enables the delivery of high-quality, whole-person MAiD care that is values-based and sustainable. A "care ecology" strategy recognizes the interconnected web of relationships and structures necessary to support a quality experience of MAiD for patients, families, and clinicians. This program exemplifies a care ecology approach that addresses common barriers to entry to MAiD practice, and also meets the needs of a variety of stakeholders through the creation of patient and family resources, team supports, standards of practice, professional development opportunities, organizational infrastructure, and community partnerships. We also describe how a thriving care ecology evolves to remain resilient, and to enable integration as the needs of the organization, team and program change over time. The design and development of this program may be adapted to other jurisdictions and organizations where MAiD is introduced, or where new patient populations become eligible for MAiD. This care ecology model may also be applicable to the creation of sustainable programs that provide other morally controversial or novel clinical services.

The fertilizer industry generates wastewater rich in phosphate and fluoride content, with concentration as high as 4540 and 9720 mg L −1 , respectively. The untreated wastewater may enhance the growth of algae, promote eutrophication, and create serious effects on environmental health and aquatic life. Therefore, this wastewater has to be treated before releasing into the environment. This study evaluates the performance of a three-compartment electrodialysis reactor to remove fluoride and calcium ions, and recover phosphate present in the wastewater, for possible further use in the fertilizer industry. The experiments were conducted in a batch system at room temperature. A 4 L of wastewater was electrodialysed using three different electrical current (i.e., 0.5, 0.75, and 1.0 A) and two different membrane surface areas (i.e., 100 and 200 cm 2 ). The highest removal of fluoride ions was up to 260 mg L −1 (2.7%) by applying 1 A of current and 100 cm 2 membrane area. No substantial increase of fluoride and calcium removal was observed for 200 cm 2 membrane area. Interestingly, the amount of the remaining phosphate was high (i.e., only 1% removal), implying a very efficient recovery in the feed. The energy required for fluoride ion transfer was much lower than for phosphate ion, i.e., up to 6 vs. 0.12 mol kWh −1 , suggesting that a higher removal of fluoride can possibly be achieved by limiting migration of phosphate ion through the membrane.

Our main purpose in this paper is first to study the interaction between capital account liberalization and political stability in affecting financial stability and so economic growth. Second, our contribution consists in decomposing both the effect of capital account liberalization and political stability into a direct effect on growth and an indirect effect through affecting financial system efficiency and stability. We show that the aggregate positive effect of political stability outweighs the negative partial or temporary effect. However, the total effect of capital account liberalization is negative and economic repressing. Our economic approach is firstly based on a growth traditional model conducted through a simple panel data regression, and then we used a logit model to identify potential determinants of financial crisis including interaction term. This methodology permits us to augment the growth model by a crisis model obtaining treatment effect specification necessary to decompose the total effect of our variables of interests. We conclude that the impact of capital account liberalization on growth depends on the political stability and that political stability is more needed to stimulate economic growth in less-liberalized countries. Capital account increases economic growth rate only in politically unstable countries where needs for capital is high.

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An improved procedure for detecting minisatellite sequences inPhaseolus vulgaris is described. Both M13 protein III tandem repeat and the 33.15 human mini-satellite sequences revealed polymorphisms with a high number of sharp bands after digestion of genomic DNA withHae III,Hinf I, orTaq I. Improved resolution of the numerous restriction fragments detected by these probes is accomplished by one or more of the following: varying agarose concentration, using high SDS hybridization buffer, exposure of the autoradiograph without intensifying screens, and transfer of the autoradiograph to electrophoresis paper. Increased stability of the DNA-DNA hybridizations with these heterologous probes is obtained by reducing hybridization temperature. Labeling probes with the polymerase chain reaction can accentuate some restriction fragments depending upon the radiolabeled nucleotide used.

Background The visualization of civil infrastructure systems and processes is critical for the validation and communication of computer generated models to decision-makers. Augmented Reality (AR) visualization blends real-world information with graphical 3D models to create informative composite views that are difficult to create or replicate on the computer alone. Methods This paper presents a scalable and extensible mobile computing framework that allows users to readily create complex outdoor AR visual applications. The technical challenges of building this reusable framework from the software and hardware perspectives are described. Results SMART is a generic and loosely-coupled software computing framework for creating AR visual applications with accurate registration algorithms and visually credible occlusion effects. While SMART is independent of any specific hardware realization, ARMOR is built as a hardware implementation of SMART to test its algorithm correctness and its adaption to engineering applications. In particular, ARMOR is a modular mobile hardware platform designed for user position and orientation tracking, as well as augmented view display. Conclusion The framework has been validated in several case studies, including the visualization of underground utilities for excavator control and collision avoidance to demonstrate SMART’s rapid creation of complex AR visual applications.

In this paper we consider one dimensional random Jacobi operators with decaying independent randomness and show that under some condition on the decay vis-a-vis the distribution of randomness, that the distribution function of the average spectral measures of the associated operators are smooth.

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This paper explores several relevant themes in a cross-racial counseling situation between a white female worker and an African-American professional woman. Issues of racial identity development, bi-culturalism, and the effects of cross-racial counseling are discussed in detail and illustrated with case material.

Recently, Internet of Things (IoT) and multimedia are gaining popularity because of their usages in various applications. Numerous sensors and automated devices are generating huge volumes of data. Therefore, it is required to efficiently and effectively analyze this voluminous data. It can be achieved by using appropriate machine leaning techniques such as clustering. Among the clustering techniques, the k-means method/algorithm is one of the simplest, effective and commonly used methods. For making the cluster, it uses a measure of similarity/distance among the data observations. Nearby/similar data observations are placed within the same cluster whereas distant/dis-similar data observations are placed in other clusters. Hence, the similarity/distance metric plays a major role on the performance and accuracy of the k-means. Therefore, using an appropriate similarity/distance metric, the performance and accuracy of the k-means can be improved. K-means algorithm is majorly implemented using Euclidean distance metric. With the objective to explore the better and/or alternate similarity/distance metric(s) for k-means, a case study, based on empirical evaluation, of thirteen different similarity/distance metrics on six well-known datasets is performed and presented in this paper. By using the efficient and effective similarity / distance metrics, the performance and accuracy of the k-means algorithm can be improved which leads to formation of good clusters of various data observations or things or images etc. The results of the empirical study are analyzed and compared on the basis of widely used statistical clustering evaluation/validation measures. Based on the comparative results, these metrics are assigned with the ranks. Overall, the results demonstrate that Manhattan and Minkowski distance metrics gives better results for k-means algorithm.

Rational B-splines have become the new standard for representing free-form curves and surfaces. This paper presents a method for approximating rational B-splines using digitised data. Instead of using the classical optimisation approach to solve the multivariable nonlinear equations, a new method based on iterations of least-squares solutions and single variable mimimisation is developed. This is made possible by modifying the original objective function to avoid the rational format. Simulation of fitting a 90° arc shows that the algorithm can produce accurate solutions close to nominal values. The efficiency of the algorithm also makes it possible to apply the method to day-to-day reverse engineering problems using rational B-splines.

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WILL you pardon me for asking a question which probably I ought to be able to answer myself? Mr. Corfield, in his interesting comparison of the hygienic performances of the ancients and ourselves, mentions the well-known Cloaca Maxima as one of the great glories of the Romans. Can he tell us how they got the sewage into it? I presume the invention of Bramah was not known in those times, and I was a little disappointed in not finding in his able paper a solution of a mystery which has puzzled me since my childhood. What did the Romans want with a Cloaca Maxima, and how did they use it?

MR. PROCTOR'S interesting paper in your last number reminded me of an essay on “The Nebular Hypothesis,” originally published in 1858, and re-published, along with others, in a volume in 1863 (“Essays: Scientific, Political, and Speculative.” Second Series), in which I had occasion to discuss the question he raises. In that essay I ventured to call in question the inference drawn from the revelations of Lord Rosse's telescope, that nebulae are remote sidereal systems—an inference at that time generally accepted in the scientific world. On referring back to this essay, I find that, besides sundry of the reasons enumerated by Mr. Proctor for rejecting this inference, I have pointed out one which he has omitted.

IN reply to J. H.'s query respecting the flight of the albatross mentioned in a paper of mine on the flight of birds, read at the November meeting of the Norfolk and Norwich Naturalists' Society, I beg to assure him that no bird is able to fly without flapping its wings.

I SHALL feel obliged if, through the medium of your widely-circulated journal, you will allow me to point out an extraordinary mistake into which Mr. Radau has fallen, in a memoir inserted in the Annales Scientifiques de I' Ecole Normale Supereure tom. vi. 1869, in which he criticises certain of my conclusions about the representation of the motion of a free rotating body contained in a paper published by me in the “Philosophical Transactions” for 1866. In his preamble, M. Radau says, speaking of the theory of rotation in connection with the names of Poinsot, Rueb, Jacobi, and Richelot:— “Tout recemment M. Sylvester a essaye d'appliquer au mene sujet des considerations nouvelles qui l'ont conduite a des resultats interessants, a cote d'autres dont l'exactitude peut etre contestee.”

YOUR correspondent G.H. will find in one of Thomson's papers something very like the assertion “that there was a time when the earth rotated too swiftly for the existence of life,” but expressed in a manner at once more precise and less pleonastic. “The existence of life” reminds me of a phrase which I heard a few days ago from a female beggar; she lamented that her husband had “fallen into habits that are habitual.” Well; the required reference is the paper “On Geological Time,” in the Transactions of the Geological Society of Glasgow, vol. iii. Part I. pp. 15 and 16 (§§ 19 and 20). A thousand million years ago, says Thomson, “there must have been more centrifugal force at the equator due to rotation than now, in the proportion of 64 to 49…. If the earth rotated seventeen times faster, bodies would fly off at the equator…. If you go back ten thousand million years ago—which, I believe, will not satisfy some geologists—the earth must have been rotating more than twice as fast as at present—and if it had been solid then [which he thinks improbable], it must be now something totally different from what it was.” Such a state of things he seems to consider inconsistent with any organic life such as we know of. Surely the connection of this question with the argument from retardation by tidal friction is too plain to need exposition.

IN an interesting paper, quoted at p. 661 of NATURE, Prof. Rolleston dwells upon the proportion of short-lived male skeletons, found in Anglo-Saxon interments, as contrasted with the older character of the Romano-British interments, deducing there-from a conclusion as to their respective longevity. The writer appears to have forgotten that the youth of Romano-Britain had for many generations been forcibly expatriated—drafted abroad to feed the armies of Imperial Rome.

DR. INGLEBY is curious to know what Prof. Helmholtz would say on this vexed question. If Dr. Ingleby will turn to page 630 of the “Physiologische Optik,” he will find that Prof. Helmholtz has anticipated his wishes. As others of your readers may be interested in seeing how the matter is treated by one who is facile princeps in this department, I subjoin a translation of the passage. If the curious experiment mentioned by Dr. Ingleby had referred only to the vertical diameter of the disc, it would have seemed to be another illustration of our inveterate tendency to ascribe an exaggerated value to vertical lines or angles, at or near the horizon. It is said that if ten men be required to fix off-hand on a star half way between the zenith and horizon, nine, at least, will choose one very much too low. If an exact square be cut out in paper and pinned against the wall opposite to the eye, the sides will appear longer than the top or bottom. If an equilateral triangle be placed in the same position, the angles at the base will appear larger than the angle at the vertex. If a line be drawn parallel to the bottom of a sheet of paper, and a second line, making with it an angle of 20° or 30°, any one attempting, without moving the paper, to draw a third line through the point of intersection, so as to make an angle with the second line equal to that which the second makes with the first, will make the second angle too large. (This experiment is guaranteed by Helmholtz.) After reading Helmholtz's theory, metaphysicians may be willing to allow that all these illusions are to be derived, after his example, from the clouds. As metaphysicians have, before now, contributed a good deal to the clouds, it is perhaps only fair that the clouds should contribute something to the metaphysicians.

IN the report of the papers read at the Academy of Sciences, Paris, June 13, which appears in NATURE for June 30, it is stated that MM. Jamin and Amaury presented a note on the above subject, in which they point out, apparently as if it were something new, that the specific heat of some of these mixtures rises even above that of water.

PROFESSOR FEE is by many years the oldest amongst living fern-authors. He has held for more than a quarter of a century the chair of botany at Strasburg, and has concentrated his attention principally upon ferns and the other allied higher orders of cryptogamic plants. He published a general treatise upon the classification of the order as long ago as 1844, ancl since then many consecutive years have never passed without producing some memoir upon the subject from his fertile pen. Having recently received a fine collection of ferns from Dr. Glaziou, the superintendent of the Botanic Gardens at Rio Janeiro, he has been stimulated to add one more memoir to the series, and that is the work now before us. All the series of his monographs, several of which are in folio, are illustrated beautifully and copiously, not only with full-sized figures of the plants, but also with careful magnified analytical details; and together they form by far the most extensive and excellent series of fern-plates which anyone upon the Continent has published. The present memoir is quite upon a par with its predecessors in this respect. It is in quarto, and contains seventy-eight quarto plates and a list of all the ferns and fern-allies known to the author as inhabiting Brazil, with a list of special stations, but with descriptions of novelties only. But there is one drawback to the value of Fee's works, and that is a very great one. Living at a distance from the great metropolitan herbaria, our author has apparently worked almost entirely upon his own private collections, and has continually failed to recognise well-known plants, and has made new species in great numbers out of the specimens which his correspondents have sent him, which no one else has been able to understand as such. In none of his works—we have no alternative but to say—has this tendency been carried to a greater excess than in the present one. For Brazil alone he describes and figures in the present memoir upwards of 180 new species, so-called. These are not from tracts of country which the collectors whose gatherings have been already reported upon have not visited, or have left unexplored, but nearly all from the vicinity of the capital, and from the gatherings of Glaziou. Now the neighbourhood of Rio Janeiro is exceedingly rich in ferns; but there is, perhaps, no other part of Tropical America from which herbaria, both in England and on the Continent, have been more bountifully supplied. The consequence is, that out of this 180 we do not think that more than from twelve to twenty species are really newj in any sense in which we understand in this country what is meant by a species. For instance, we have some seven or eight species elaborately characterised and figured from what cannot be called anything else than so many individual fronds of that most cosmopolitan of ferns, our common English Aspidium or Polystichum aculeatum. Or, to take one of the exclusively Brazilian species, Cyathea Gardneri, a very distinct tree-fern, is included in the list under five different names—Gardneri (Dr. Gardner's number on which Hooker described the species quoted), incurvata (a name of Kunze's published in the Linnaea from Regnell's specimens), mamillata, taunaysiana and attenuata, the last three new species here named and figured for the first time; but the figures, beautiful as they are, might, any of them, have been drawn from Gardner's specimens. The author does not seem to have any knowledge of numerous English and German books and papers in which Tropical American ferns are described, as for instance, Grisebach's excellent Flora of the British West Indies; and this leads to further name-crossing. In short, although one cannot but admire the excellence and the copiousness of the illustrations in these memoirs, and ought not to leave out of sight the example of devotedness to science which they show, expenditure of time devoted to one object through a long course of years, and of money, only a very small, proportion of which their sale can possibly repay, yet still the predominant feeling on the mind must needs be that to deal with plants in this way has a direct tendency to bring species-botany at a very rapid rate into a state of utter confusion. Cryptogames Vasculaires du Bresil. Par Prof. A. L. Fee avec le concours de Monsieur le Dr. Glaziou. Pp. 268, 4to., 78 Plates. (Paris: Bailliere.)

THE soul of many an anti-Darwinian will have been cheered by Mr. A. W. Bennett's paper on “The Theory of Natural Selection from a Mathematical Point of View.” It is, in fact, a very admirable piece of special pleading, based on a skilful assumption of premisses which, to a careless or biassed observer, might seem indisputable.

I AM forcibly reminded of Pope's lines, A little knowledge is a dangerous thing: Drink deep, or taste not, the Pierian spring, by the argument used by Mr. Bennett in the P.S. to his letter in NATURE, of the 24th November, in which he says, after quoting a passage from a paper by Mr. Jenner Weir: “Here at least it would seem as if imperfect mimicry was anything but beneficial to the individual; how can the principle of natural selection account for its propagation in these instances?” He considers that a little mimicry is a dangerous thing. I would rather agree with Lord Brougham in his remark on the above lines, that as a little knowledge is better than great ignorance, so a little mimicry is better than great dissemblance.

THE papers read by me before the Entomological Society “On the Relation between the Colour and the Edibility of Lepidoptera and their Larvae” having been noticed and commented upon by Mr. A. W. Bennett and others in NATURE, I have deemed it desirable to offer a few remarks on the subject.

ALLOW me space for a word or two in reply to Mr. Wallace and Mr. Butler's observations on my papers on Mimicry and Hybridisation.

UNDER this heading, in your issue of 5th inst., you report a paper by Prof. Osborne Reynolds, M.A., read at a meeting of the Manchester Literary and Philosophical Society, Nov. 29 last. This paper sets forth that the tails of comets, the solar corona, the aurora, and the Zodiacal lights are due to the ether which “fills” space. Comets' tails, as stated by the Professor, in his paper, are an effect due to the medium through which it passes being heated and illuminated by the comet; and that the other phenomena are also due to the ether.

THIS is the first part of a new periodical established primarily for the publication of the results of the observations made at the Botanico-Physiological Institute at Breslau. The part contains five papers on different microscopic algae and fungi, and their pathological effects. In subsequent numbers it is intended to give priority to botanical observations which relate to biological questions, or which are more or less connected with practical natural science, medicine, agriculture, &c. It is hoped that the publication may fill the place formerly occupied by Karsten's “Botanische Untersuchungen.” Beitrage zur Biologie der Pflanzen. Herausgegeben von Dr. Ferdinand Cohn. Erster Heft. Mit sechs zum theil farbigen Tafeln. (Breslau, 1870. London: Williams and Norgate.)

Recent links between computer science and synthetic biology allow for construction of many kinds of algorithmic processes within cells, obtained either by a direct engineered design or by an evolutionary search. In the latter case, horizontal gene transfer and especially transfer of plasmids by conjugation is generally respected as a crucial source of genetic diversity in bacteria. While some previous studies focused on mutations as the crucial principle to obtain diversity for engineered evolution, here we consider conjugation itself as a tool to generate diversity from a pre-determined library of biocircuits basic components. The recent development of CRISPR-Cas9 and its programmable DNA cutting ability makes it a powerful selection tool able to remove nonfunctional biocircuits from a cell population. In this paper, we describe a framework for controlled bacterial evolution of biocircuits based on conjugation and on CRISPR-Cas9, resulting in a direct biological implementation of an evolutionary algorithm. In silico experiments provide data to estimate the computational/search capability of plasmid-based engineered evolution.