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The taxonomy, diversity, and distribution of the aquatic insect order Trichoptera, caddisflies, are reviewed. The order is among the most important and diverse of all aquatic taxa. Larvae are vital participants in aquatic food webs and their presence and relative abundance are used in the biological assessment and monitoring of water quality. The species described by Linnaeus are listed. The morphology of all life history stages (adults, larvae, and pupae) is diagnosed and major features of the anatomy are illustrated. Major components of life history and biology are summarized. A discussion of phylogenetic studies within the order is presented, including higher classification of the suborders and superfamilies, based on recent literature. Synopses of each of 45 families are presented, including the taxonomic history of the family, a list of all known genera in each family, their general distribution and relative species diversity, and a short overview of family-level biological features. The order contains 600 genera, and approximately 13,000 species.
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)