Heterogeneous Assemblage Research Articles

Organic matrixlike macromolecules associated with the mineral phase of sea urchin skeletal plates and teeth.

The skeletal plates and teeth of the echinoid Paracentrotus lividus contain a heterogeneous assemblage of macromolecules that are not part of the connective tissue, but are presumably intimately associated with the mineral phase. Upon dissolution of the Mg-calcite mineral phase, some of these molecules are insoluble. The insoluble fractions of the teeth and skeletal plates are quite different, the former being predominantly protein and the latter, primarily some unknown nonproteinaceous material. The soluble constituents are similar in both tissues. These hydrophilic macromolecules have been partially separated and characterized. In both hard parts, two distinct classes of macromolecules are present, as indicated by the amino acid compositions of their protein constituents. These two classes of macromolecules are also present in the shells of a foraminifer and in various mollusks, both of which are formed by the "organic matrix-mediated" biomineralization process. The locations of these macromolecules in the teeth and skeletal plates are not known, nor whether they form coherent structures. It is therefore premature to conclude that these macromolecules do function as an organic matrix, although the results presented are in agreement with such an interpretation.

Lithostratigraphy of the basal Waitemata Group, Kawau Subgroup (new), Auckland, New Zealand

Abstract The basal strata (Otaian, early Miocene) of the Waitemata Group in the Auckland region of northern New Zealand consist of a 10–45 m thick, heterogeneous assemblage of shallow marine sediments, distinct from the overlying, deep-water sandstone and siltstone that form the bulk of the group. In the north they partly fill depressions in the underlying, highly irregular greywacke surface, and in the south form a veneer over the more planar, eroded Te Kuiti Group surface. Kawau Subgroup is proposed for all the basal Waitemata Group rocks that crop out from Cape Rodney in the north to Raglan in the south and Cape Colville in the east. Three formations are recognised: (1) Papakura Limestone (much enlarged) = lenses of pebbly, gritty, shelly or sandy bioclastic limestone and local limestone breccia with associated thin lenses of shelly sandstone and conglomerate. Three members are described—Motuketekete Limestone, Purser Limestone, and Te Akau Members (all new); (2) Tipakuri Sandstone Formation (new) = le...

Studies of Carboniferous Fungi. II. The Structure and Organization of Mycocarpon, Sporocarpon, Dubiocarpon, and Coleocarpon (Ascomycotina)

The problematic organism, Sporocarpon, was among the first fossil fungi to be described. The genus was actually a heterogeneous assemblage of fungal forms, and was eventually divided into several taxa including Sporocarpon, Dubiocarpon, and Mycocarpon. In the present paper these organisms, as well as a similar, previously undescribed genus, Coleocarpon; are described from Lower, Middle, and Upper Pennsylvanian strata in North America, and from Upper Carboniferous sediments in England. Although initially considered to be radiolarian-like protozoa, these structures show far more similarity to ascomycetous cleistothecia. All forms are ornamented, spherical bodies with a complex wall which encloses scattered asci and ascospores. Taxa are distinguished primarily by differences in the organization of the cleistothecial wall. Structurally similar organisms are found today among the Eurotiales.

STUDIES OF CARBONIFEROUS FUNGI. II. THE STRUCTURE AND ORGANIZATION OF MYCOCARPON, SPOROCARPON, DUBIOCARPON, AND COLEOCARPON (ASCOMYCOTINA)

The problematic organism, Sporocarpon, was among the first fossil fungi to be described. The genus was actually a heterogeneous assemblage of fungal forms, and was eventually divided into several taxa including Sporocarpon, Dubiocarpon, and Mycocarpon. In the present paper these organisms, as well as a similar, previously undescribed genus, Coleocarpon; are described from Lower, Middle, and Upper Pennsylvanian strata in North America, and from Upper Carboniferous sediments in England. Although initially considered to be radiolarian‐like protozoa, these structures show far more similarity to ascomycetous cleistothecia. All forms are ornamented, spherical bodies with a complex wall which encloses scattered asci and ascospores. Taxa are distinguished primarily by differences in the organization of the cleistothecial wall. Structurally similar organisms are found today among the Eurotiales.

A new look at variation in Darwin's species of acorn barnacles

Darwin's studies on barnacles, begun to satisfy his curiosity about specimens from the Beagle, but later extended to the large collections of other naturalists, lasted for 8 years and produced a set of definitive monographs. Darwin was particularly troubled over the taxonomy of two groups of acorn barnacles, Balanus tintinnabulum and B. amphitrite, which he ultimately classified as clusters of wellmarked varieties. Recent studies, based on established taxonomic methods or on statistical treatment of morphometric data, suggest these are clusters of full species and that the ‘intermediate’ forms are just phenotypic variants. Darwin was also troubled by the small chthamalid intertidal barnacles, which he eventually grouped as varieties of a world-wide species, Chthamalus stellatur. Gel electrophoresis and morphometrics now show this to be a heterogenous assemblage of distinct species, some very different, others closer together, all with restricted geographical range, but all showing extreme variability in the characters normally used for classification. Darwin's difficulties with the classification of the highly varying barnacles, and his anatomical studies on these peculiar animals, must have had considerable influence on the development of his theories about natural selection, more than is usually acknowledged by writers on evolution. These ‘lost years’ were in fact a period of intense zoological enquiry, and Darwin's change in attitude with regard to species and variation in nature underwent a big change, as can be seen from the letters and from the differences between the early drafts written before the barnacle work and the later Natural Selection and The Origin. Whether we regard the difficult groups of Balanus as clusters of species or clusters of varieties, they still draw attention to evolutionary processes as in Darwin's day.

Early Evolution of Reptiles

exploitation of the terrestrial environment. Following the achievement of these features, the early amniotes underwent a major radia­ tion. The fossil record of early amniotes is complete enough to establish their relationships to the major groups living today. It also provides an opportunity to consider the evolutionary processes associated with a period of major radiation. Early amniotes may be viewed today as a phylogenetically heterogeneous assemblage (or paraphyletic group), for they include the ultimate ancestors of mammals and birds, as well as of the modem squamates, crocodiles and turtles. Yet, within the context of the Paleozoic, they were a monophyletic group, with a close common ancestry. To judge by the general similarity of their skeletal anatomy to that of modern lizards and crocodiles, they probably had a broadly similar physiology as well. Amniotes appear suddenly in the fossil record, without any recognized predecessors (9). They are first known from the early Pennsylvanian (West­ phalian B) deposits of Joggins, Nova Scotia, within the stumps of upright lycopods (11). This peculiar mode of burial favors the preservation oftruly terrestrial animals and explains the absence of either reptiles or plausible terrestrial ancestors in older fossil localities that were the result of more normal, subaqueous deposition.

Character, distribution, and tectonic significance of accretionary terranes in the Central Alaska Range

The central part of the Alaska Range near Mount McKinley is composed of nine separate tectonostratigraphic terranes that were accreted in southern Alaska during late Mesozoic time. These terranes now form long, linear, fault‐bounded belts that are subparallel to the Denali fault on the north but oblique to the fault on the south. The postaccretion right lateral offset along the Denali fault system is about 200 km. From north to south the major terranes are (1) Yukon‐Tanana terrane, metasedimentary and metavolcanic rocks, mostly undated, but including rocks of known late Paleozoic age; polymetamorphosed with terminal events in late Mesozoic, (2) Pingston terrane, isoclinally folded Upper Triassic deep‐water silty limestone, quartzite, and carbonaceous slate, folded with upper Paleozoic phyllite, chert, tuff, and minor limestone, (3) McKinley terrane, upper Paleozoic flysch, chert, and minor limestone, intruded by large gabbro sills and dikes and overlain by thick piles of Triassic porphyritic pillow lava; the top of the section is thick sequence of upper Mesozoic conglomerate, flysch, chert, and phyllite, (4) Dillinger terrane, very thick sequence of strongly folded lower Paleozoic micaceous sandstone (turbidites), graptolitic shale, and deep‐water limestone, locally overlain unconformably by Jurassic fossiliferous sandstone or Triassic (?) pillow basalt, (5) Windy terrane, heterogeneous assemblage of serpentinite, basalt, tuff, and chert (= ophiolite?) with Paleozoic and Mesozoic flysch and blocks of mid‐Paleozoic fossiliferous limestone, (6) Mystic terrane, predominantly upper Paleozoic flysch and conglomerate, but also includes lower Paleozoic graptolitic shale, pillow basalt, and shallow‐water limestone, and upper Paleozoic fossiliferous limestone, sandstone, chert, and undated pillow basalt, (7) Chulitna terrane, Upper Devonian ophiolite overlain by upper Paleozoic chert, volcanic conglomerate, limestone, and flysch, capped by Lower Triassic limestone and Upper Triassic red beds, basalt, and interbedded basalt and limestone; later Mesozoic rocks are sandstone, chert, and argillite, (8) Westfork terrane, Jurassic chert, sandstone, conglomerate, and Triassic (?) and Jurassic crystal tuff, (9) Broad Pass terrane, upper Paleozoic chert, tuff, and argillite, with blocks of Devonian and older limestone locally associated with serpentinite. These diverse terranes, of mixed oceanic and continental affinities, are now juxtaposed to form a complex sequence of folded and faulted rootless nappes. Major suture zones between them are occupied by intensely deformed upper Mesozoic flysch. All of the terranes differ markedly from Wrangellia, the southermost coherent accreted terrane in Alaska. Paleomagnetic measurements from Triassic rocks prove that Wrangellia originated near the equator, probably in the southern heimsphere. Paleolatitudes for terranes in the central Alaska Range are not yet determined, but other lines of evidence (biogeographic and lithologic) suggest large‐scale northern transport for some terranes.

RHODOPHYCEAN PIT PLUGS: AN ULTRASTRUCTURAL SURVEY WITH TAXONOMIC IMPLICATIONS

The fine structure of pit plugs was examined in 63 species of red algae representing 34 families. The number of plug cap layers was found to be a taxonomically reliable character when tested against a recent revision of the Rhodymeniales which established the order Palmariales. In a broader survey involving all the orders of red algae possessing pit plugs, three basic plug cap configurations were detected. These differ in having one, two, or no plug cap layers. Some taxa have plug caps in which the outer cap layer is greatly elaborated, however, this layer was shown to be positionally and cytochemically identical, thus probably homologous, to the outer cap layer of the typical two‐layered plug cap. The pit plug character confirms the validity of the order Palmariales and indicates that the Nemaliales and Cryptonemiales are heterogeneous assemblages. Revision of these groups along lines indicated by the plug character is supported by significant features of morphology and reproduction. These correlations lead us to propose that Rhodophysema and Coriophyllum be transferred to the Palmariales, that the Gelidiales be resurrected, that the Bonnemaisoniales (including the Naccariaceae) is deserving of recognition, that the Batrachospermaceae be raised to a higher rank which will also receive the Lemaneaceae and the Thoreaceae, and that the Corallinaceae and Hildenbrandiaceae both be raised to ordinal status.

Seasonal Changes and Overwintering of Parasites in the Bat, Myotis lucifugus (Le Conte), in a Wisconsin Hibernaculum

During 1979-1980, eight digenetic trematode species, one cestode species and three nematode species were recovered from the little brown bat (Myotis lucifugus) at a southeastern Wisconsin hibernaculum. Statistically significant seasonal variation was observed for two digenetic trematodes. Mean densities and prevalence (%So of hosts infected) of parasites were highest in autumn and spring and lowest in summer. Highest species number occurred in autumn. Greater density and prevalence in autumn and spring may be correlated with bat swarming and emergence patterns, behavioral phenomena which would also produce a more heterogeneous assemblage of parasites during these times of the year. Myotis lucifugus retained high densities and prevalence of parasites throughout 8 months of hibernation.

A review of the genus Tristania R. Br. (Myrtaceae): a heterogeneous assemblage of five genera

The genus Tristania is reviewed, with particular emphasis on the Australian species, on the basis of morphological and anatomical evidence and, as a result, divided into five genera. The genus Tristania R.Br. em. Schott is monotypic, the genera Welchiodendron and Ristantia are newly described and Lophostemon Schott and Tristaniopsis Brongn. & Gris are reinstated from synonymy. One new species, Tristaniopsis collina, is described and 33 new combinations made: Welchiodendron longivalve, Ristantia pachysperma, Lophostemon confertus, L. grandijlorus ssp. grandiflorus and ssp. riparius, L. Iactifluus, L. suaveolens, Tristaniopsis anomala, T. beccarii, T. bilocularis, T. burmanica, T. clementis, T. decorticata, T. elliptica, T. exiliflora, T. ferruginea, T.fruticosa, T. grandifolia, T. laurina, T. littoralis, T. macrosperma, T. merguensis, T. micrantha, T. oblongifolia, T. obovata, T. oreophila, T.pentandra, T. polyandra, T.pontianensis, T. razakiana, T. rufescens, T, stellata and T. whiteana. Two further species, Tristania psidioides and Tristania umbrosa, are transferred to Xanthostemon.

Influence of potassium source (sediment vs. open water) and sediment composition on the growth and nutrition of a submersed freshwater macrophyte ( Hydrilla verticillata) (L.f.) Royle)

Potassium uptake by Hydrilla verticillata (L.f.) Royle from sediment versus overlying water was evaluated in relation to the K demands incurred by this species during an 8-week period of growth. The investigation was conducted on a heterogeneous assemblage of sediments and in two solutions differing fundamentally in the presence (2.3 mg l −1) and absence of K. Both biomass production and shoot morphology in Hydrilla varied significantly between solutions and among sediments. In contrast to N and P, which were readily mobilized from most sediments, K was mobilized from all sediments to only a minor extent by this species. Mobilization of K was proportional to interstitial water K concentration; yet on at least four of the six sediments examined, K supplied from sediments was insufficient to support the maximal growth of Hydrilla. The open water rather than the sediment appears to be the primary source of K supply to this species and perhaps to most other submersed freshwater macrophytes. Where K was supplied in solution, sediment-related differences in the growth of Hydrilla negatively correlated with sediment organic matter content over the range 0.2–56.2% dry sediment mass. It is tentatively suggested that the organic composition of sediments may influence the species composition of aquatic macrophyte communities.

Geologic Investigations in the Cayman Trough: Evidence for Thin Oceanic Crust along the Mid-Cayman Rise

The Mid-Cayman Rise is a 110 km long accreting plate boundary (~ 2cm/yr, full rate) characterized by a deep rift valley. Eighteen transponder-navigated dives were made by the submersible ALVIN along the rift valley walls in two areas on opposite sides of the rift valley. The relief of the walls is produced by a large number of inward facing small-throw fault escarpments with vertical displacements ranging from a few tens of meters to perhaps as much as 400 m. From these escarpments 142 samples were collected, and gabbroic rocks (116 samples), characterized by a wide range of compositions and a complex metamorphic history, predominate in number over other rock types (basalt, serpentinized ultramafic). We interpret the assemblage of rocks exposed on the escarpments to indicate that a shallow level magma reservoir exists beneath the axis of accretion at the Mid-Cayman Rise and creates anomalously thin oceanic crust with a carapace of only several hundreds of meters of diabase and basalt. This carapace is underlain by a plutonic assemblage, possibly of only 1 to 2 km thickness, composed of gabbroic rocks intruded by screens of serpentinized ultramafic. The crust created along the axis of the Rise may be thin as a result of the juxtaposition of the short, slowly accreting Rise segment and two long transform faults. The closely spaced transforms act as heat sinks for the asthenosphere wedge rising beneath the axis of accretion, resulting in a decrease in the volume of melt segregated from the asthenosphere and, hence, a thinner than normal oceanic crust. Although the Mid-Cayman Rise probably represents an end-member example of this effect, we suggest that thin oceanic crust and the existence of a heterogeneous assemblage of gabbroic rocks at shallow levels is a characteristic of ridge/transform intersections at slowly accreting plate boundaries.

Morphologic variability of Pennsylvanian lyginopterid seed ferns

The current level of understanding of the morphological variability of Pennsylvanian lyginopterid seed ferns is reviewed. This group of pteridosperms that ranges throughout the Carboniferous is represented by a heterogeneous assemblage of stems, leaves, ovules and pollen organs. Vegetative organs have been useful in tracing the origin of the eustele from a protostele, while the fern-like fronds appear to have had their origin from a non-planated branching system. The small radially symmetrical ovules, while exhibiting some diversity in the organization of integument, demonstrate little apparent alteration in pollen-receiving mechanisms and reproductive versatility. Lyginopterid pollen organs are synangiate and include both radial and bilateral forms. The stratigraphically earliest types are radial and borne upright on naked branches, while later forms are usually bilateral and typically associated with laminar foliage. Pollen is morphologically and structurally similar to the spores of many ferns, and probably germinated through the proximal suture. The apparent homogenous nature of lyginopterid seed ferns may indicate that relatively little evolution had taken place over a long geological time span. However, evidence from some compression floras suggests that far more diversity exists within the order in a non-swamp environment than had previously been thought. Current concepts about lyginopterid pteridosperms that have been developed from a small group of plants in a relatively homogeneous environment may need considerable revision as we learn more about the non-swamp inhabiting forms.

Thrust emplacement of the Schoonover sequence, northern Independence Mountains, Nevada

Research Article| October 01, 1981 Thrust emplacement of the Schoonover sequence, northern Independence Mountains, Nevada ELIZABETH L. MILLER; ELIZABETH L. MILLER 1Department of Geology, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar JAMES BATESON; JAMES BATESON 1Department of Geology, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar DAVID DINTER; DAVID DINTER 1Department of Geology, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar JAMES R. DYER; JAMES R. DYER 1Department of Geology, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar DWIGHT HARBAUGH; DWIGHT HARBAUGH 1Department of Geology, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar D. L. JONES D. L. JONES 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94325 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1981) 92 (10): 730–737. https://doi.org/10.1130/0016-7606(1981)92<730:TEOTSS>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation ELIZABETH L. MILLER, JAMES BATESON, DAVID DINTER, JAMES R. DYER, DWIGHT HARBAUGH, D. L. JONES; Thrust emplacement of the Schoonover sequence, northern Independence Mountains, Nevada. GSA Bulletin 1981;; 92 (10): 730–737. doi: https://doi.org/10.1130/0016-7606(1981)92<730:TEOTSS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Preliminary paleontologic data from the northern Independence Mountains, Nevada, suggest that at least part of the Schoonover sequence is time equivalent to the lithologically and structurally similar upper Paleozoic Havallah sequence. The base of the Schoonover is a major thrust fault that juxtaposes paleogeographically distant but, in part, time-equivalent rocks. Along the west side of the range, the Schoonover sequence structurally overlies Late Mississippian nonmarine to shallow-marine rocks that unconformably overlie deformed Ordovician strata of the Roberts Mountains allochthon. This nonmarine to shallow-marine sequence is correlative to overlap assemblage sequences elsewhere in Nevada. Along the east side of the range, the Schoonover is thrust over shallow-marine to slope-facies Permian rocks that unconformably overlie deformed lower Paleozoic miogeoclinal rocks as well as the Roberts Mountains allochthon.The allochthonous Schoonover sequence is a heterogeneous assemblage of deformed deep-water sedimentary rocks and greenstone units. Isoclinally folded chert in the structurally lower half of the Schoonover yields ages based on radiolaria that range from earliest Mississippian to possibly latest Devonian at the very base of the sequence to as young as Early Pennsylvanian in structurally higher parts of the sequence. Clastic rocks within the lower part of the sequence contain debris derived from erosion of Roberts Mountains allochthon-type rocks. Rare volcaniclastic and volcanogenic units in the Schoonover indicate an andesitic-dacitic source. The structurally higher part of the allochthon contains a thick succession of silty-limestone turbidite deposits that represent yet a third, carbonate source terrane for the Schoonover sequence.Structural data indicate southeast-directed thrusting of the Schoonover sequence. Thrusting postdates deposition of Late Permian rocks and is inferred to predate intrusion of Late Jurassic plutons present to the north of the map area. Similarity of structural style and constraints on the timing of thrusting in the Independence Mountains strongly suggest that the Schoonover sequence may represent the northeasternmost exposures of the Golconda allochthon.The age of at least some of the pelagic sediments in the Schoonover sequence may overlap the age of the youngest rocks known in the Roberts Mountains allochthon as well as the age of the Antler Orogeny. This suggests that the Schoonover sequence was deposited, at least in part, in a location that was paleogeographically distant from the edge of the Nevadan portion of the North American shelf during the Antler Orogeny. No volcanism occurred on the continental shelf during the emplacement of the Roberts Mountains allochthon; therefore, the presence of tuffaceous turbidites within the Schoonover also suggests deposition far away from the continental margin. On the other hand, the composition of coarse clastic rocks within the Schoonover is compatible with their derivation from the eroding Roberts Mountains allochthon, suggesting proximity to the North American shelf. If sedimentary rocks from dual sources (volcanic arc and Roberts Mountains allochthon) are indeed interbedded in the Schoonover, rather than tectonically interleaved, then this might argue in favor of deposition of the Schoonover-Havallah sequences in a back-arc basin setting. This content is PDF only. 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The whalebill is a stork

THE avian order Ciconiiformes contains a heterogeneous assemblage of long legged, long necked birds which have traditionally been classified together because of superficial resemblance. The order usually contains the storks, ibises, herons and two rather aberrant birds, the whalebill (Balaeniceps rex) and the hammerkop (Scopus umbretta), which are placed in monotypic families, the Balaencipitidae and Scopidae, respectively. The evolutionary relationships among the members of the Ciconiiformes and between this order and other living birds are little understood. Using an analysis of the morphology of the stapes (the single avian ear ossicle)1,2, I have obtained evidence for the evolutionary affinity of the whalebill with the storks, which now seem to form a monophyletic assemblage.

Cladostrobus and the systematics of cordaitalean leaves

Cladostrobus Zalessky, 1918, is a male strobilus with spirally arranged microsporophylls, having a rhomboid lamina and a long stalk. The sporangia occur in groups. Microspores are of monosaccate type and are without a haptotypic mark. The name Cladaitina dibnerae gen. et sp. nov. is introduced for isolated spores of this kind. Cladostrobus may be a male strobilus of plants that bore Rufloria leaves. The group Cordaitales, as known now, comprises a heterogeneous assemblage of incompletely known plants, mostly sterile leaves. An artificial classification is proposed for sterile leaves, similar to the one already in vogue for dispersed spores and pollen. This classification is in fact a key for identification and cataloguing, and is not meant to show natural affinities.

The Reunion of Setcreasea and Separotheca with Tradescantia American Commelinaceae: I

Elsewhere (Hunt, i973), I have suggested that the species assigned to Setcreasea K. Schum. & Sydow would be better disposed as two sections or series within Tradescantia L., the genus from which the original species were taken. The justification for this point of view arises partly from re-examination of Setcreasea itself, and partly from synoptic study of the tribe Tradescantieae, where generic limits have been drawn with increasing fineness in recent years. The latter aspect of the case will be briefly considered first. The tribe Tradescantieae Meisn. as redefined by Rohweder (1956) contained 13 genera, resulting from the gradual dismemberment of Tradescantia L. itself and Callisia L. Since Rohweder's paper, further genera have been recognized by H. E. Moore (1958, 1962), Leiandra Rafin. and Hadrodemas H. E. Moore, which, with the addition of Cuthbertia Small, whose position is controversial, and Separotheca Waterfall, bring the total to 17. According to Brenan (1966) such dismemberment has been 'undoubtedly necessary'. Despite the process of dismemberment, however, Tradescantia itself remains a heterogeneous assemblage: the 50 or so species it contains (out of about 130 in the tribe as a whole) are a residual mass of species containing, in the writer's opinion, about eight groups and isolated species worthy of rank equivalent to many of the putative genera already proposed. In the final analysis, dismemberment will only be complete when the North American T. virginiana group (about 20 closely related species, fide Anderson & Woodson) is all that is left in Tradescantia.

Melting Relations of Brown-Hornblende Mylonite from St. Paul's Rocks under Water-Saturated and Water-Undersaturated Conditions to 30 Kilobars

Crystalline brown-hornblende mylonite, with a composition similar to some basanites and nephelin-ites, was crushed and reacted with excess water and with no water added (about 2% water present) in sealed platinum capsules in a piston-cylinder apparatus from 10-30 kb. The solidus with excess water, and liquidus curves for excess water and for 2% water, are presented, together with stability limits (within 50°C brackets) in the melting intervals for amphibole, plagioclase, clinopyroxene, garnet, olivine, rutile, nepheline, and zoisite. With increasing water content and consequent decreasing liquidus temperature on the water-undersaturated liquidus surface, the number of liquidus and near-liquidus minerals increases, the field of olivine extends to higher pressures, and garnet becomes stabilized at pressures above 20 kb. Orthopyroxene was not found. Amphibole is stable at the liquidus between 10 and 21 kb with excess water at 1,075°C, and between 10 and 16 kb with 2% water at 1,175°C. These results combined with previous interpretations are consistent with the following tentative petrogenetic history for St. Paul's Rocks. A water-undersaturated olivine-basanite magma rose from a depth of about 100 km at a temperature of 1,200-1,300°C, and differentiated until it reached a depth somewhere between 45-70 km, where the magma had reached the composition of brown-hornblende mylonite. At a temperature between 1,050°C and 1,000°C amphibole was the dominant mineral being precipitated. Exsolution of water from the magma became fixed in the mantle peridotite as amphibole, and locally may have caused incipient melting of the peridotite. This process may have initiated upward movement of the heterogeneous assemblage of peridotite and largely crystallized basanite magma, which rose as a near-solid diapiric intrusion with temperature possibly remaining as high as 1,000°C up to 7 km deep, where intense mylonitization began during the final ascent and shallow emplacement.

Combined autogenous and anautogenous ovarian development in individual Culex tarsalis Coq. (Dipt., Culicidae)

AbstractThe ability to mature eggs without feeding on blood (autogeny), occurring in most populations of Culex tarsalis Coq., approaches an incidence of 50% in the Bakersfield, California strain. Females that were not allowed to lay eggs matured autogenously would occasionally feed on blood but much less readily than anautogenous females. When such females did feed on blood, additional eggs started maturing in other follicles. This produced a heterogeneous assemblage of eggs, some matured autogenously in primary follicles interleaved with others in secondary follicles (on other ovarioles) that matured following the blood-meal. During or soon after autogenous maturation of eggs in some primary follicles, the contemporary primary follicles were resorbed, forming ovariolar dilatations, a condition commonly interpreted as signifying a parous condition.

Changes in testicular leydig cells and in plasma testosterone levels among seasonally breeding rock hyrax.

Seasonal changes in plasma testosterone levels and in various testicular parameters were studied in 41 adult male rock hyrax (Procavia habessinica). Among animals collected during the annual breeding season, testis weights and plasma testosterone levels were approximately five times greater than among animals collected outside the breeding season. Light microscopic measurements showed that increase in testis weight was largely due to enlargement of the seminiferous tubules. Histological sampling techniques indicated no significant change in Leydig cell numbers. Leydig cell size increased during the breeding season, and average Leydig cell volume showed significantly positive correlation with plasma testosterone level. With the electron microscope, Leydig cell hypertrophy was seen to involve changes in quantity and structure of several cytoplasmic constituents. Lipid droplets disappeared and smooth endoplasmic reticulum (SER) spread dramatically as the cells increased in size. In contrast to the sparse and heterogeneous assemblage of irregularly tubular and cisternal SER seen in nonbreeding animals, the extensive masses of SER in breeding animals appeared as relatively straight, unbranched tubules of uniform diameter. Peculiar membranous structures, possibly derived from the SER, were abundant in the periphery of Leydig cells from animals with high plasma testosterone levels. These findings suggest that there is a definite relationship between plasma testosterone levels and Leydig cell fine structure in seasonally breeding hyrax.