Intermediate Specimens Research Articles

A New Amphisbaenian from Cuba

-A new species of Amphisbaena is described from the Cabo Cruz region of eastern Cuba. It shares with two other Cuban species, Amphisbaena barbouri (new rank) and A. cubana, fusion of the second supralabial and ocular scales. It is a pallid, long-tailed, xerophilic species associated with dry, coastal limestone habitats. In the West Indies, amphisbaenians occur only on the island banks of Cuba, Hispaniola, and Puerto Rico (Schwartz and Henderson, 1991). Three species are currently recognized from Cuba: Amphisbaena blanoides, A. palirostrata, and A. cubana. The first two occur in western Cuba and were placed in the genus Cadea until recently (Hedges, 1996; Powell et al., 1996). A fourth taxon, barbouri, was described as a subspecies of A. cubana (Gans and Alexander, 1962). It has a peculiar distribution in west-central Cuba in that it is known only from coastal or near-coastal localities in the north (Havana-Matanzas) and south (Bay of Pigs-Cienfuegos). Specimens from east and west (including Isla de Juventud) of these areas are assigned to the nominate subspecies (Schwartz and Henderson, 1991) and no morphologically intermediate specimens are known despite the close proximity of some localities and apparent sympatry at Soledad, Cienfuegos Province (Gans and Alexander, 1962). For these reasons (and, see below), we choose to recognize A. barbouri at the species level. During July, 1994, we collected along the south coast of eastern Cuba (Oriente) in the provinces of Granma and Santiago de Cuba. Although the entire coast between Cabo Cruz in the west and Cabo Maisi in the east is generally dry, the areas near the two capes are more xeric 3Author for correspondence and reprints. E-mail: sbhl@psu.edu than the intermediate coast. In the western xeric area (Meseta de Cabo Cruz), between Cabo Cruz and Boca del Toro, a series of limestone terraces descends stepwise to the coast, and the xeric scrub vegetation grows within solution holes in the limestone. The conditions are very reminiscent of the xeric, scrub-covered, terraced limestone on the southern part of the Barahona Peninsula in Hispaniola. Within a kilometer to the west of Boca del Toro we collected four specimens of a distinctive, slender, pale species of Amphisbaena. A fifth specimen of this new species, also from the Cabo Cruz region, was found among specimens of A. cubana in the collection of the University of Michigan Museum of Zoology. MATERIALS AND METHODS Scale counts were taken according to the criteria of Gans and Alexander (1962); measurements of head scales were taken with a dissecting microscope and digital readout micrometer caliper. The count of total half-annular segments of the head is a count of the segments dorsal to the splitting of the second body annulus into two half-annuli, which may be given as a total count (the number of segments in anterior halfannulus + number of segments in posterior half-annulus). Snout-vent length (SVL) and tail measurements were taken to the nearest mm by laying the specimen along a ruler. Other length measurements were made with a digital readout micrometer caliper and recorded to the nearest 0.1 mm. Drawings of head scalation 92 This content downloaded from 157.55.39.180 on Mon, 25 Apr 2016 06:02:31 UTC All use subject to http://about.jstor.org/terms NEW CUBAN AMPHISBAENIAN FIG. 1. Amphisbaena carlgansi, from the type-locality in Granma Province, Cuba. were made with a camera lucida attachment to a Wild dissecting microscope. Museum abbreviations follow standardized usage (Leviton et al., 1985), except for MNHNCU, which refers to the collection of the Museo Nacional de Historia Natural (Havana, Cuba). Amphisbaena carlgansi, sp. nov. Figs. 1-2 Holotype.-MNHNCU 4421, a female, taken on the second limestone terrace above the sea, within 1 km west of Boca del Toro, Granma Province, Cuba, ca. 50 m. Collected on 8 July 1994 by Richard Thomas; fixed in 80-90% ethanol. Original field tag number 193876.

内装材料の目地・工法が燃焼性状におよぼす影響の評価 : 中間規模燃焼試験の提案

The influence of joint and construction details of wall assembly on the combustion behavior of linings were evaluated using 590mm × 530mm intermediate specimens in this paper. From the results of this study, it is possible to estimate the influence of joint and construction details of wall assembly on the combustion behavior of linings by intermediate burning test using intermediate scale specimen.

96/04384 Follar uptake of 137Cs from the water column by aquatic macrophytes

Outcrossing in the aquatic genus Nymphoides (about 50 species) is promoted by various sexual conditions including dimorphic heterostyly (most species) and dioecy (four species). In eastern North America, Nymphoides aquatica and Nymphoides cordata are dioecious sister species that differ only slightly by their leaf pigmentation and texture, adventitious root form, and overall size. Although these features distinguish most individuals, the occurrence of morphologically intermediate specimens within broadly overlapping geographic ranges often confounds their identification. Hybridization of these taxa has not been documented previously, yet the potential exists for gene flow between N. aquatica and N. cordata because of their similar floral morphology, reliance on outcrossing, and partial sympatry. We studied individuals collected across the ranges of N. aquatica and N. cordata, using morphological data and nuclear (ITS) and chloroplast (matK/trnK) molecular sequence data, to better ascertain their distinctness and to investigate further the possibility of hybridization. Quantitative morphological data supported the existence of two species that are broadly diagnosable across several measurements, although approximately seven percent of specimens analyzed remained undiagnosed under our criteria. Molecular phylogenetic results indicated that most individuals of N. aquatica and N. cordata were readily identifiable to one or the other species, and these corresponded to reciprocally monophyletic groups. However, molecular cloning revealed that some individuals collected within the sympatric range of N. aquatica and N. cordata were interspecific hybrids, and these individuals on average were morphologically intermediate between the two parental species. These data are consistent with a taxonomic concept that accepts two fundamentally distinct Nymphoides species, nevertheless with some individuals being morphologically intermediate, at least partly as a result of natural interspecific hybridization.

96/04388 The greenhouse gas consequences of wasre management — identifying preferred options

Outcrossing in the aquatic genus Nymphoides (about 50 species) is promoted by various sexual conditions including dimorphic heterostyly (most species) and dioecy (four species). In eastern North America, Nymphoides aquatica and Nymphoides cordata are dioecious sister species that differ only slightly by their leaf pigmentation and texture, adventitious root form, and overall size. Although these features distinguish most individuals, the occurrence of morphologically intermediate specimens within broadly overlapping geographic ranges often confounds their identification. Hybridization of these taxa has not been documented previously, yet the potential exists for gene flow between N. aquatica and N. cordata because of their similar floral morphology, reliance on outcrossing, and partial sympatry. We studied individuals collected across the ranges of N. aquatica and N. cordata, using morphological data and nuclear (ITS) and chloroplast (matK/trnK) molecular sequence data, to better ascertain their distinctness and to investigate further the possibility of hybridization. Quantitative morphological data supported the existence of two species that are broadly diagnosable across several measurements, although approximately seven percent of specimens analyzed remained undiagnosed under our criteria. Molecular phylogenetic results indicated that most individuals of N. aquatica and N. cordata were readily identifiable to one or the other species, and these corresponded to reciprocally monophyletic groups. However, molecular cloning revealed that some individuals collected within the sympatric range of N. aquatica and N. cordata were interspecific hybrids, and these individuals on average were morphologically intermediate between the two parental species. These data are consistent with a taxonomic concept that accepts two fundamentally distinct Nymphoides species, nevertheless with some individuals being morphologically intermediate, at least partly as a result of natural interspecific hybridization.

The Guelph PIXE software package II

Modifications and improvements made to the software package GUPIX in the period since it was first described in 1989 are reported. The code now handles thin, intermediate, thick and multi-layer specimens, and permits the inclusion of “invisible” elements and complexes that may be independent or stoichiometrically related to elements whose X-rays are visible in the spectrum. M X-rays have been added to the data base, and are included in secondary fluorescence computation. The nonlinear least squares spectrum fitting procedure has been altered to conclude with a linear least-squares section which provides better reproducibility. The conventional statistical weighting has been augmented by a systematic weighting scheme that deals with uncertainties in low-energy tailing features on the spectral peaks. A new, exact treatment of peak area errors gives good agreement with the earlier approximate approach. The influence of the digital filter used to remove spectrum background upon errors and detection limits is examined, and recommendations provided on the appropriate filter dimensions. Input and output options have been expanded, and various minor changes made.

Hybrid crinoids in the fossil record (Early Mississippian, Phylum Echinodermata)

Potential hybrid fossil crinoids, Eretmocrinus magnificus x Eretmocrinus praegravis, are identified from the Lower Mississippian Fort Payne Formation of south-central Kentucky. These are the first fossil hybrid crinoids identified, and one of very few examples of hybrids recognized in the fossil record. Eretmocrinus magnificus x E. praegravis specimens have shapes and calyx plate sculpturing that are morphologically intermediate between well-defined, distinct parent species. Suspected hybrids occur at localities where parent species co-occur and where the parent species are the most abundant; the hybrids occur at what may have been the distributional margins of the parent species; and the mixture of characters on suspected hybrids seems to be morphogenetically partitioned. Parent species are derived from separate lineages within Eretmocrinus, and hybridization is the most probable explanation for these morphologically intermediate specimens. This example highlights the need to consider hybridization as a potential interpretation of intermediate morphologies among fossils and raises questions concerning the impact of hybridization for our interpretation of the fossil record and the role of hybridization in the evolutionary process.

有機酸塩熱分解法により作製したBi系酸化物焼結超伝導体の特性と組織

The Bi-base high-TC oxide superconductors have been synthesized by thermal decomposition of organic acid salt. This process does not require strict pH control unlike other chemical preparation process, facilitating an easy preparation of oxide superconductors. Furthermore, this process allows an uniform and quantitative addition of other elements. The precursor powders less than 10 μm in diameter have been obtained by this process. The powders prepared by the present process exhibit TC’s over 100 K in a shorter sintering time than those prepared by the conventional powder process.The effects of intermediate process, e.g. pressing and grinding between heat-treatment cycles, on superconducting properties and grain morphologies were investigated. The TC’s are appreciably increased by an intermediate pressing, and reduced by intermediate grinding. The TC of 109 K has been obtained by intermediate pressed specimens, with total heat-treatment time of 60 h. The maximum JC (77 K) so far obtained in the sintered specimen is 1540 A/cm2.The X-ray diffraction analyses performed on these specimens reveal that the intermediate pressing enhances the diffraction peaks of high-TC phase, with strong (00l) orientation, and suppresses those of low-TC phase. Meanwhile, the diffraction peaks of high-TC phase are reduced by the intermediate grinding. The changes in TC and JC by the intermediate pressing and grinding have been discussed relating to the structure changes. The Bi-base oxide powders prepared by the present process may be useful for the conductor fabrication.

Clinal Morphological Variation along a Depth Gradient in the Living Scleractinian Reef Coral Favia pallida: Effects on Perceived Evolutionary Tempos in the Fossil Record

The Holocene reef-building coral Favia pallida was sampled at 4.5 m depth increments (to 40 m) from two reefs on Enewetak Atoll to examine intraspecific environmental effects. An exposed outer reef was massive and wall-like, whereas a sheltered lagoonal reef grew as a slender pinnacle. Corallite diameter and growth rate, two attributes retrievable in fossil corals, were measured with data partitioned into shallow ( 29 m) subsets. Highly significant differences between depth zone populations were found for both corallite diameters and growth rates in analyses of individual and combined reef data sets. Canonical variates analyses (CVA) separated populations from depth zones along single, highly significant, functions. Centroids and 95% confidence intervals, calculated from CVA scores of colonies in each population, are widely separated for the lagoon reef and combined data sets. Conversely, populations from shallow and intermediate depths on the outer reef display overlapping confidence bars indicative of more gradational morphologic changes. When CV's were used to classify specimens to groups, misassignments of intermediate depth specimens to shallow or deep-water populations underscored the gradational nature of the environment. Completely intergrading populations of Favia pallida collected from different depths can be morphologically separatedmore » into statistically distinct groupings. A stratigraphic succession of such morphotypes might be interpreted as abruptly appearing separate species if sampling were not as uniform, systematic, and detailed as was possible on modern reefs. Analyses of evolutionary patterns must carefully assess potential effects of clinal variation if past evolutionary patterns are to be interpreted correctly.« less

Population genetics and biochemical systematics of marsh flies in the Sepedon fuscipennis group (diptera: sciomyzidae)

An isozyme comparison of 23 loci among two subspecies of the Sepedon fuscipennis Loew group and a population of S. fuscipennis “intermediate specimens” indicated that six loci were monomorphic in all three populations. The F-statistics showed moderate differentiation among the populations ( F ST-0.127) with high values for AK and 6-PGD only. Neís index (1978) of genetic identity for the three populations ranged from 0.923 to 0.990, indicating a high degree of similarity among all populations. Mean heterozygosity ranged from 0.135 to 0.201 with an average of 0.163 across the three populations. Our genetic data, as well as previously described morphological data, suggest that this is a single species showing geographic cline in several character states, rather than well-defined subspecies.

Root Architecture of Shrubs and Saplings in the Understory of a Tropical Moist Forest in Lowland Panama

Entire root systems of 2-3 m tall plants in tropical moist forest near Barro Colorado Island, Panama were excavated and measured. We studied 3-4 plants, each, of the canopy and subcanopy species Trichilia tuberculata (Meliaceae), Prioria copaifera (Caesalpinoideae), Hirtella triandra (Chrysobalanaceae), and Tetragastris panamensis (Burseraceae); the immature treelet Faramea occidentalis (Rubiaceae); and the mature shrubs Piper cordulatum (Piperaceae), Psychotria horizontalis (Rubiaceae), and Hybanthusprunifolius (Violaceae). Root and crown architecture of intermediate specimens was illustrated. Shrubs had shallower root systems with a higher proportion of total surface area at 0-20 cm depth than tree saplings. Shrubs also had greater root surface area, both absolutely and relative to leaf area. An analysis of Coster's data for 6-month old plants of 44 species grown in a Javanese garden confirmed that shrubs tend to have relatively shallower root systems than tree species. We examine several explanations of differing root architecture for these life forms based on adult requirements for water, support, and nutrients. We speculate that reproduction creates greater nutrient demands in shrubs than in saplings. By analogy with community patterns on very poor soils, a well developed, superficial root system increases nutrient absorption from the relatively richer upper stratum. The tradeoff appears to be reduced resistance to water stress in shrubs compared with tree species.

Plumage, Morphometric, and Song Variation in Mourning (Oporornis philadelphia) and Macgillivray's (O. tolmiei) Warblers

Plumage, Morphometric, and Song Variation in Mourning (Oporornis philadelphia) and Macgillivray's (O. tolmiei) Warblers

Gouania axilliflora (Rhamnaceae), a New Species from Peru

The new species, Gouania axilliflora, is described from the province of Cajamarca, Peru. The resemblance to the Brazilian Alvimiantha tricamerata Grey-Wilson is discussed. The genus Gouania L., comprising a few dozen species of tendriliferous, tropical vines, is more in need of revision than any other genus of Rhamnaceae. After 20 years of desultory study, I estimate that of the more than 60 specific epithets proposed for American species, fewer than 25 will survive a critical revisionary study. And I predict that even after critical revision, the distinctions between the survivors will continue to be weakened by the presence of intermediate specimens only arbitrarily referable to one or another recognized species. That is to say that most species of the genus are poorly differentiated. It is therefore remarkable to find, among recent Peruvian collections, a species so distinctive that one could make a case for the erection of a new genus. I have no hesitation in proposing this new taxon even in the absence of information on the base of the plant or the mature fruits. Gouania axilliflora M. C. Johnst., sp. nov. (fig. 1.-TYPE and only known collection: Peru, Department of Cajamarca, Province of Cajabamba, Condebamba valley, CajabambaCajamarca road, 78?9'W, 7?33'S, 2600-2100 m, 15 Feb 1983, D. N. Smith & R. Vdsquez M. 3396 (holotype: TEX!; isotypes: AMAZ, CPUN, HUT, MO!, USM). Plantae scandentes cirrhiferi, caulibus costatis sulcatis hispidis; petioli 2-4 mm longi; laminae foliorum anguste elliptico-ovatae 15-25 mm longae 7-11 mm latae, mucronatae, supra fere glabrae venatione impressa, subtus hispidae venis lateralibus 2 costaque prominentibus valde campto-acrodromis; stipulae 4-5 mm longae; axillae distales 2-florae; pedunculi pedicellique sub anthesi nulli; sepala ? 1 mm longa; petala 0.7-0.9 mm longa cuneata exunguiculata spathulata incisurata; discus glaber tenuis planus integer; styli rami ?0.6 mm longi; fructus (non satis maturus) ? 6 mm longus ? 5 mm diametro exalatus. Vine [fide collectors]; stems slender, with 8 relatively strong nearly hairless ribs alternating with 8 weaker ribs, the 16 grooves bearing dense, longitudinally oriented, crisped white, translucent hairs 0.4-1 mm long, each hair more or less appressed basally and weakly spreading distally; tendrils slender, 3-5 cm long, hooklike to tightly coiled. Leaves: petioles 2-4 mm long; blades narrowly elliptic-ovate, 15-25 mm long, 7-11 mm wide, adaxial surface more or less hairless and dull olive green and with impressed venation, abaxial surface between major veins with sparse hairs 0.4-0.9 mm long and with prominent venation including midrib and 2 arcuate lateral primaries departing midvein at extreme base of blade and conspicuously acrodrome to mucronate tip of blade; stipules linear, 4-5 mm long, deciduous. Inflorescence: 2-flowered glomerules in distal axils; flowers green, essentially sessile at anthesis; cupular structure at base of flower (interpreted as an expanded receptacle) hemispherical, about 1.5 mm in diameter at anthesis, densely hairy externally, adnate to side of ovary; sepals 5, triangular, about 1 mm long and wide, hairy abaxially, glabrous adaxially, falling sooner or later after anthesis or rarely persisting on younger fruit; petals 5, yellow-green(?), 0.7-0.9 mm long, cuneate but not clawed, distally broadened and spatulate, concavo-convex and hooding anthers, hairless, tip-notched about 0.1-0.2 the total length; filaments 5, about 0.3 mm long, anthers about 0.3 mm long; disk hairless, thin, flat, covering top of ovary and extending as an extremely narrow thin unlobed flange at the periphery of the top of the ovary; style-branches 3, clavellate, about 0.6 mm long, excurved. Fruit (not perfectly mature) about 6 mm long, about 5 mm in diameter, 3-angled, wingless (at this stage of maturity, at least); fruiting pedicels up to 4-5 mm long; ma-

Effect of Grain Size on Strength, Ductility and Fracture in Recrystallized Ni<SUB>3</SUB>Al Doped with Boron

Tensile tests at room temperature were performed on recrystallized Ni3Al doped with boron having grain sizes from 1.6 to 208 μm to determine the effect of grain size on the strength, ductility and fracture. Both yield and flow stresses depend on grain size in agreement with a Hall-Petch relation when the specimen size effect is taken into account. The increase in Hall-Petch slope with strain is explained in terms of the difference in work-hardening rate for different grain sizes. The increase of lattice friction stress with strain is found to be analogous to the single crystal properties.While the {111} cracking is predominant without necking for coarse-grained specimens, the slant-type fracture and cup-cone fracture preceded by a necking is mainly observed for intermediate and fine-grained specimens, respectively. Large elongation is developed when the intersection of slip bands becomes insufficient to produce the {111} cracking, and the void formation which results in the cup-cone fracture is retarded.

Melanism in the spider Pityohyphantes phrygianus (C. L Koch): the genetics and the occurrence of different colour phenotypes in a natural population

In the sheetweb spider Pityohyphantes phrygianus (C. L. Koch) there is a continuous variation in dark colouration. The specimens may be divided into three main phenotype classes of colouration; pale, intermediate and melanic. Analyses of the genetic basis of colour variation in P. phrygianus showed that a polygenic system is probably involved. The narrow heritability of dark colouration was estimated as 0·43 (±0·25), based on parent-offspring regression using mid-parent and mean offspring scores. A small-scale laboratory experiment indicated that the melanics may have an activity—and hence a foraging—advantage over non-melanics at low temperatures. A temporal variation in the frequencies of the three main phenotype classes was observed in a natural population in SW Sweden. This variation was due to differences between the proportion of pale and intermediate specimens in three cohorts; the proportion of melanics was low in all samples, averaging 3·7 per cent.

Natural Hybrids of the Freshwater Sculpins Cottus bairdi and Cottus cognatus (Pisces: Cottidae): Electrophoretic and Morphometric Evidence

Natural hybrids of the sculpins Cottus bairdi and C. cognatus in the Sus- quehanna River drainage are electrophoretically identifiable on the basis of at least seven enzyme loci. Identification of Cottus hybrids on morphological grounds is, how- ever, somewhat speculative. Meristic characters overlap widely between the parental species, and hybrids generally do not possess intermediate character states. Hybrids can be tentatively identified on the basis of their intermediacy for two diagnostic characters which unambiguously distinguish the two species elsewhere in the Susque- hanna drainage: presence/absence of the palatine tooth patch, and number of pelvic fin rays. Principal component and discriminant analyses of suspected hybrids and samples of the parental species show the presumed hybrids to be somewhat intermedi- ate in morphology but to largely resemble C. cognatus in body form and meristic counts. Diagnostically intermediate specimens are more variable in their meristic and mensural characters than are nonintermediate individuals, and also display more bi- lateral asymmetry. F2 and backcross progeny were not detected in electrophoresis samples, but morphological evidence suggests that some introgression may be occur- ring.

Effects of Space Shuttle Exhaust Plumes on Gills of Some Estuarine Fishes: A Light and Electron Microscopic Study

The first few launches of the space shuttle resulted in fish kills in a lagoon near the launch site. To study this phenomenon further, sheepshead minnow (Cyprinodon variegatus), sailfin molly (Poecilia latipinna), and mosquitofish (Gambusia affinis) were exposed to the exhaust plume in buckets placed near the launch site. An open bucket provided a full exposure, a partly closed one provided an intermediate exposure, and a closed one was the control. Three h after launch, the pH of the water from the full exposure had decreased from about 7 to about 3, Al and Fe levels had increased, and some fish had died. Gills ol most fishes from full exposures and some from intermediate exposures were damaged. Gills, however, exhibited no aneurysms, mucus coagulation, or hemorrhaging. Some secondary lamellae swelled, some fused with adjacent lamellae, and others clubbed or retracted into the filament. Many lamellar pavement cells died and sloughed off. Mucous cells of intermediate exposure specimens bulged on the filament surface and pavement cells lost their microridges. Mineral deposits, probably aluminum oxide, occurred on gills of fishes from full exposures. Focally, pavement cells were eroded exposing the underlying structures. The sudden pH drop in the full exposures probably caused the gill damage. However, we could not determine the effect of previous exposure on the experimental fish, or whether gill damage was the lethal lesion. The possibility is indicated that some fish recover after exposure to the exhaust plume.

Problems of Species Identity in the Lake Ontario Seulpins Cottus bairdi and C. cognatus

The sculpins Cottus bairdi and C. cognatus are difficult to distinguish in Lake Ontario because intermediate specimens are present and because C. bairdi in the lake is more variable than C. bairdi from the surrounding drainage basin. Our evidence indicates that intermediates are probably the products of hybridization between C. bairdi and C. cognatus. The greater variability of C. bairdi in Lake Ontario may be due to subspecies differences, but we suggest that backcrossing of C. bairdi with hybrids would also account for this phenomenon.Key words: sculpin, Lake Ontario, taxonomy, hybridization

The taxonomic status of Timmia sibirica

A critical study of the differentiating features of the North American populations of Timmia sibirica Lindb. et Arnell and T. norvegica Zett. reveals that populations with structure intermediate between these two taxa occur. Although from widespread localities, the intermediate specimens seem limited in number and T. sibirica and T. norvegica quite commnonly occur in mixed populations with no evidence of any intergradation. Therefore, it is concluded that the two taxa ought to be regarded as distinct species. The taxonomically important character-states of upper leaf cells and costa of T. sibirica. T. norvegica, and of the intermediate populations are illustrated with scanning elecron micrographs. The habitat of T. sibirica, like that of T. norvegica, is invariably on strongly calcareous substrates adjacent to waterfalls, along streams, or in low-lying tundra. The North American distribution of T. sibirica is mapped, including previously unreported localities as far south as 51° N in the Canadian Rocky Mountains.

The effects of thermal pre-treatment and molecular weight on the impact behaviour of polycarbonate

Notched impact fracture experiments have been conducted on specimens of polycarbonate in three different conditions, (a) as received, (b) annealed at 125° C, and (c) electron beam irradiated to reduce the molecular weight. By consideration of the behaviour of a wide range of notch geometries four different failure modes were identified which were present in different proportions for each material. (1) Razor notched specimens failed in a completely brittle manner, well described by linear elastic fracture mechanics. (2) Small notch tip radii specimens failed in an apparently brittle manner through the formation of a single craze. (3) Some intermediate notch tip radii specimens failed in a predominantly brittle manner with small shear lips indicative of plane stress yielding. A fracture mechanics approach was used here, the measured toughness correlating with the extent of plane stress yielding. (4) Fully ductile failure was observed for large notch tip radii for all materials. It has been established that the embrittlement of polycarbonate caused by annealing is due to an increase in the yield stress, whereas that caused by reducing the molecular weight is due to a reduction of the crazing stress. In both cases, more specimens of intermediate notch tip radius are caused to fail in the low energy brittle mode designated (2) above. By varying the yield stress and crazing stress independently we have thus been able to distinguish clearly how both influence the brittle-ductile transition.

Evidence from double infestations for the specific status of human head lice and body lice (Anoplura)

Abstract Samples of head lice and body lice obtained from Ethiopians suffering from double infestations were mounted onto microscope slides and measured. The mean length of body lice (♀ 4.4mm; ♂ 3.8mm) was greater than that of head lice (♀ 3.5 mm; ♂ 2.9mm), but the best discriminant was the length of the tibia of the middle leg (♀ 425/296 μ♂421/291 μ). No intermediate specimens were found in these double infestations, although intermediates can can be produced experimentally by cross‐mating. Since populations of head lice and body lice remain distinct it is concluded that they represent two distinct species, Pediculus capitis De Geer and P. humanus Linneaus.