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A multi-part theorem is presented concerning the morphogenesis of high-symmetry structures made of three-dimensional morphological units (MU's) free to move on the surface of a sphere. All parts of each MU interact non-specifically with the remainder of the structure, via an isotropic function of distance. Summing all interactions gives a net figure of merit, X, that depends upon MU positions and orientations. The structure evolves via gradient dynamics, each MU moving down the local gradient of I. The analysis is reresented with generality in Fourier space, which eases the expression of symmetry. Structures near symmetry, but far from a local minimum of I, are analyzed. For each, a symmetrical configuration can be found, for which X is an extremum with respect to symmetry-breaking perturbations. Under gradient dynamics, a quadratic measure of such deviations from symmetry decreases monotonically, anywhere in the large basin of attraction of a local minimum. Thus: high symmetry is an attractor. Application is made to icosahedral virus capsids. The Symmetrization Theorem shows that a stable capsid, maintained by non-specific interactions among its capsomeres, could arise generically in a "bottom-up" process. For animated evolutions that selfassemble into high symmetry, visit http://www.albany.edu/~cmarzec/
Comparing the modern level in the biology of gastrointestinal stem cells with that achieved in the hemopoietic stem cell studies, we can say, using Till's expression (1982), that at present the "morphological phase" in the investigations of the former is continuing. Still urgent is the problem of morphological verification of presumable stem cells in colonic crypts and gastric glands. Also important is to clarify the ways of renewal of the well-differentiated but low proliferating activity endocrine cells, the chief cells of the fundic glands, and the cells of Brunner's glands. Further studies of interaction between epithelial and stromal cells are needed. The knowledge of relationships between stem cells and their differentiated "neighbors" in the niches, as well as of peculiarities of contacts between epithelial cells proper and of the cells with the basement membrane is of major importance. It is also necessary to clarify the mechanisms of the stem cells "anchoring" as well as of the disturbances of this important property during carcinogenesis. Briefly summarized below are the most essential, in our opinion, directions of the study of stem cells; some of these have already been started, whereas others can only be predicted. 1. The isolation from normal tissues of the fractions of intact cells enriched with the stem cells, with their subsequent culture. 2. The clarification of the factors governing the regulation of renewal of stem cells: specific stimulators and inhibitors of proliferation; and characterization of the receptor apparatus of stem cells, particularly for the enteropancreatic hormones. 3. The antigenic characteristic of stem cells. 4. The study of molecular peculiarities of DNA replication of clonogenic cells. 5. The molecular aspects of commitment and differentiation of stem cells. 6. The quantitative and qualitative characteristics of stem cells in the process of carcinogenesis. 7. The qualitative evaluation of the dynamics of formation and disappearance of carcinogenic DNA adducts in stem cells. 8. The clarification of interspecies features of stem cells as well as of their morphogenetic potentialities in onto- and phylogenesis. 9. The characterization of metaplastic changes in stem cells.
The present paper is a continuation of "The Birds of the Galapagos Islands, with Observations all the Birds of Clipperton and Cocos Islands (Columbiformes to Pelecaniformes)". The collection of land bird skins brought back by the Expedition numbers 5,916, exclusive of the Galapagos Dove. The writer lacks the time to study this large number of specimens and therefore deems it advisable to publish his field notes without further delay. In addition to the skins, considerable collections of eggs, nests, and birds and stomachs in alcohol were macle. These also await investigation. The land birds of Cocos Island, Costa Rica, and of the Galapagos Islands are treated in the present connection, with the exception of the Galapagos Dove already considered in the earlier paper. The sequence and nomenclature of species in both papers is that of Sharpe's "Hand-list of the Genera and Species of Birds." As the species of the genera Geospiza and Camarhynchus demand a thorough revision with all available material at hand, the writer uses provisionally, with a few changes, the specific names as defined by Messrs. Rothschild and Hartert and Messrs. Snodgrass and Heller. Wherever the writer fails to recognize a species admitted by these authors, the rejected name is placed in a. selected synonymy. The localities listed for each species also include those mentioned by Messrs. Salvin, Ridgway, Rothschild and Hartert, and Snodgrass and Heller. For a full, description of the botanical regions or zones (dry or arid, moist or humid, and grassy, in order from seashore to mountain top) mentioned in this paper, the reader should refer to Mr. Alban Stewart's paper "A Botanical Survey of the Galapagos Islands."
This paper is a general review of the problem of clutch-size in birds. It grew out of a search through the literature to see to what extent clutch-size trends found in the Robin, Erithaau8 rebecula, might apply generally. Part I. describes those types of clutch-size variation found within any species, Part II. provides a general discussion of the factors involved. In Part IlI, which follows separately later, some of the differences between different species of birds will be considered. Examples are taken mainly from European birds, hence this review is in some ways supplementary to that on African birds by Moreau (1944), to which the present study owes a considerable debt.
On Urnatella gracilis
(1893)
Evidence from archaeological fish bone assemblages from the southern North Sea region of Europe is used to illuminate fishing, fish consumption and fish trade from the 1st to the 16th century AD. The fish species represented in the material indicate a very strong influence from the local fish fauna at almost all sites. The species and size of the fish indicate that several fishing methods have been employed throughout the period studied, including nets, hooks and weirs. A chronological development in fishing, for example, a tendency towards more sea-going fishing, is reflected in the fish bone assemblages in some countlres. Evidence from fishing in the Baltic region from the 5th century BC to the 16th century AD is included in the discussion. Indications of fish trade include bones of exotic species (for instance, matinc species at inland sites) and an unbalanced representation of skeletal clements (trade with decapitated stockfish or gillless hering). Of particular interest are assemblages which indicate a fish industry, for instance, large-scale processing (removal of gills) of herring in 13th century Denmark.
Observations on fish scales
(1913)
El yacimiento de Lezetxiki (Gipuzkoa, País Vasco, España) encierra en sus 10m. de sedimentos una serie interesante de niveles musterienses culminados por otros del Paleolítico Superior. Son los niveles musterienses el objeto de este estudio. La excavación, dirigida por J.M. DE BARANDIARAN entre 1956 y 1968 permitió establecer ocho niveles (I-VIII). Estudios multidisciplinares -sedimentológicos, paleontológicos, palinológicos, antropológicos e industriales-, nos permiten acercarnos a la historia de una de las más antiguas presencias humanas constatadas en el País Vasco. Este estudio pretende situar Lezetxiki en los códigos metodológicos al uso integrándose en las referencias de las provincias culturales cántabra y aquitana. La secuencia muste dense de Lezetxiki se inicia en una fase templada del Riss con la aparición de un húmero humano neanderthalense. El nivel VII acoge las primeras industrias humanas; presencias esporádicas en una época fría en la que dominan los restos de oso y otros carnívoros sobre los ungulados, caza habitual del hombre. El nivel VI refleja un momento templado y húmedo, con desarrollo de amplios bosques de frondosas. Un bagage de utensilios lítico y óseo muy variado relaciona este nivel con el Musteriense Tlpico, que debió desarrollarse en el interglaciar de Eém (Riss-Würm). Durante las oscilaciones del Würm antiguo se dan en Lezetxiki las ocupaciones del nivel V, Iría en la base que contiene el material arqueológico, con industrias parecidas al nivel anterior aunque ahora se cazan especies menores, y el nivel IV que por primera vez refleja una frecuentación repetida de la cueva. La industria lítica es' ahora distinta, mostrando piezas de bordes muy reaprovechados y dominio de raederas que adscriben este nivel al Charentiense. A destacar la presencia de reno, la permanencia de Pliomys lenki y el predominio de ciervo. Todavía son frecuentes los osos y los carnívoros lobo, zorro y pantera. El nivel III conoce oscilaciones climáticas que reflejan la sedimentología y los pólenes, presencia de fauna fría -rinoceronte lanudo, reno, marmota- y más templada -castor, ciervo, bisonte-o Hay restos de hogares y restos humanos atribuidos al hombre de Neanderthal. La industria no presenta ningún paralelismo con las facies clásicas y todos los datos apuntan a que bien los procesos tafonómicos o la complejidad en la identilicación del depósito debido a los buzamientos cruzados del relleno (N-S y W-E) impiden más precisiones. En este nivel se da un claro predominio del equipamiento musteriense -a nivel técnico y tipológico- con importante presencia de materiales netamente auriñacienses. Cierran la secuencia un nivel Gravetiense (el 11) y otro Magdaleniense Final (el 1).
The first key is completed for the Palaearctic Pristiphora Latereille, 1810 species. Pristiphora araratensis sp. n. is descdbed. Pristiphora kamtchatica Malaise, 1931, Pristiphora mesatlantica Lacourt, 1976 and Pristiphora amelanchieris (Takeuchi, 1922) are new synonyms of Pristiphora insularis Rohwer, 1910.
A survey of the freshwater fishes of the Sepik River system of northern Papua New Guinea was undertaken by the authors between 1978 and 1985 with the use of gill nets and rotenone, and also by monitoring catches at local villages and markets. We also include records of past expeditions, namely that of the Dutch naturalist Gjellerup in 1910 and the yacht Illyria in 1929. The total known freshwater fauna as reported herein consists of 57 species in 35 genera and 23 families. The fauna is typical of other sections of New Guinea and northern Australia in that it is dominated by catfishes (Ariidae and Plotosidae), rainbow fishes (Melanotaeniidae), gudgeons (Eleotrididae) and gobies (Gobiidae) which collectively comprise 57 percent of the total species. With the exception of 22 widely distributed species that are frequently estuarine dwellers and are confined to the lower Sepik, the fishes are strongly endemic, either to the Sepik-Ramu drainages (which interconnect during Doods), or the "intermontane trough" composed of the combined Markham, Ramu, Sepik, and Mamberamo systems. Individual accounts, including brief descriptions and information pertaining to habitat, distribution and biology are included for each species. In addition illustrations are provided for many of the endemic species.
Das Untersuchungsgebiet und seine Gewässer werden beschrieben und die Ergebnisse ungefähr zehnjähriger Sammeltätigkeit für vier Ordnungen aquatischer Insekten zusammengefaßt. Die Nachweise von 68 Steinfliegen, 157 Wasserkäfern und 173 Köcherfliegen werden in Artenlisten aufgeführt. Für eine Reihe ausgewählter Arten werden neben den faunistischen Angaben einige taxonomische, zoogeographische und ökologische Hinweise gegeben. Von den Eintagsffiegen werden 39 Taxa besprochen. Eine Steinfliegen- und sieben Köcherfliegenarten sind neu für die bayerische Fauna; Crunoecia kempnyi MORTON und Prolonemura austriaca THEISCHINGER wurden erstmals für Deutschland nachgewiesen.
Presented herein is the first morphological analysis of turtle relationships to examine the monophyly of many turtle groups by using only single species as terminals and by integrating a large number of primitive fossil taxa. The data matrix consists of 136 osteological parsimony informative characters with 169 derived character states for 45 fossil and 22 living species of the clade TESTUDINATA. The results corroborate the monophyly of a large number of previously hypothesized clades, but refute the accepted hypothesis regarding the basal split of living turtles. In particular, the primitive turdes Proterochersis robusta, Kayentachelys aprix, Mongolochelys efremovi, Meiolania platyceps, and Kallokibotion bajazidi are removed from their current position as crown turtles and placed along the phylogenetic stem of this clade. The age of the turtle crown is thereby adjusted from the Late Triassic to the Late Jurassic, which is relevant to testing molecular clock hypotheses. This revised topology has important implications for the evolution of several character complexes, because it implies that the common ancestor of all living turtles must have had a partially braced brain case and a primitive trochlear mechanism. Other noteworthy conclusions include the tentative exclusion of protostegids from CHELONIOIDEA, the placement of Platysternon megacephalum outside of CHELYDRIDAE, and the tentative interpretation of Sandownia harrisi as a basal eucryptodire.