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We use seismic refraction data to investigate the firn structure across a suture zone on the Amery Ice Shelf, East Antarctica, and the possible role of glacier dynamics in firn evolution. In the downstream direction, the data reveal decreasing compressional-wave velocities and increasing penetration depth of the propagating wave in the firn layer, consistent with$\sim$1 m firn thickening every 6 km. The boundary between the Lambert Glacier unit to the west and a major suture zone and the Mawson Escarpment Ice Stream unit to the east, is marked by differences in firn thicknesses, compressional-wave velocities and seismic anisotropy in the across-flow direction. The latter does not contradict the presence of a single-maximum crystal orientation fabric oriented 45–$90^{\circ }$away from the flow direction. This is consistent with the presence of transverse simple shear governing the region's underlying ice flow regime, in association with elevated strain along the suture zone. The confirmation and quantification of the implied dynamic coupling between firn and the underlying ice requires integration of future seismic refraction, coring and modelling studies. Because firn is estimated to cover$\sim$98% of the Antarctic continent any such coupling may have widespread relevance to ice-sheet evolution and flow.

Ground-penetrating radar data acquired in the 2016/17 austral summer on Sørsdal Glacier, East Antarctica, provide evidence for meltwater lenses within porous surface ice that are conceptually similar to firn aquifers observed on the Greenland Ice Sheet and the Arctic and Alpine glaciers. These englacial water bodies are associated with a dry relict surface basin and consistent with perennial drainage into an interconnected englacial drainage system, which may explain a large englacial outburst flood observed in satellite imagery in the early 2016/17 melt season. Our observations indicate the rarely-documented presence of an englacial hydrological system in Antarctica, with implications for the storage and routing of surface meltwater. Future work should ascertain the spatial prevalence of such systems around the Antarctic coastline, and identify the degree of surface runoff redistribution and storage in the near surface, to quantify their impact on surface mass balance.

We describe elongate, wet, subglacial bedforms in the shear margins of the NE Greenland Ice Stream and place some constraints on their formation. Lateral shear margin moraines have been observed across the previously glaciated landscape, but little is known about the ice-flow conditions necessary to form these bedforms. Here we describe in situ sediment bedforms under the NE Greenland Ice Stream shear margins that are observed in active-source seismic and ground-penetrating radar surveys. We find bedforms in the shear margins that are ~500 m wide, ~50 m tall, and elongated nearly parallel to ice-flow, including what we believe to be the first subglacial observation of a shear margin moraine. Acoustic impedance analysis of the bedforms shows that they are composed of unconsolidated, deformable, water-saturated till. We use these geophysical observations to place constraints on the possible formation mechanism of these subglacial features.

Short chain chlorinated paraffins (SCCPs) are complex mixtures of polychlorinated n-alkanes, shown to bioaccumulate but with unknown effects in wild birds. The present study examined development-related effects of SCCPs on captive American kestrels (Falco sparverius) treated in ovo on embryonic day (ED) 5 by injection with technical Chloroparaffin® (C

A new three-finger toxin nakoroxin was isolated from the cobra Naja kaouthia venom, and its complete amino acid sequence was established. Nakoroxin belongs to the group of "orphan" toxins, data on the biological activity of which are practically absent. Nakoroxin shows no cytotoxicity and does not inhibit the binding of α-bungarotoxin to nicotinic acetylcholine receptors of muscle and α7 types. However, it potentiates the binding of α-bungarotoxin to the acetylcholine-binding protein from Lymnaea stagnalis. This is the first toxin with such an unusual property.

Pine Island Glacier (PIG) in the Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS) is losing mass and contributing to global sea-level rise at an accelerating rate. Although recent observations and modeling have identified the incursion of relatively warm Circumpolar Deep Water (CDW) beneath the PIG ice shelf (PIGIS) as the main driver of this ice-mass loss, the lack of precise bathymetry limits furthering our understanding of the ice-ocean interactions and improving the accuracy of modeling. Here we present updated bathymetry and sediment distribution beneath the PIGIS, modeled by the inversion of aerogravity data with constraints from active-source seismic data, observations from an autonomous underwater vehicle, and the regional gravity-anomaly field derived from satellite gravity observations. Modeled bathymetry shows a submarine ridge beneath the middle of PIGIS that rises ∼350 to 400 m above the surrounding sea floor, with a minimum water-column thickness of ∼200 m above it. This submarine ridge continues across the whole width of the 45-km wide ice shelf, with no deep troughs crossing it, confirming the general features of the previously predicted sub-ice-shelf ocean circulation. However, the relatively low resolution of the aerogravity data and limitations in our inversion method leave a possibility that there is an undetected, few-kilometers-wide or narrower trough that may alter the predicted sub-ice-shelf ocean circulation. Modeled sediment distribution indicates a sedimentary basin of up to ∼800 m thick near the current grounding zone of the main PIG trunk and extending farther inland, and a region seaward of the submarine ridge where sediments are thin or absent with exposed crystalline basement that extends seaward into Pine Island Bay. Therefore, the submarine ridge marks the transition from a thick sedimentary basin providing a smooth interface over which ice could flow easily by sliding or sediment deformation, to a region with no to little sediments and instead a rough interface over which ice flows mainly by deformation. We hypothesize that the post-Last Glacial Maximum retreat of PIG stabilized at this location because of the spatial transition in basal conditions. This in turn supports the hypothesis that the recent retreat of PIG was strongly forced, probably by changes in ocean circulation, rather than occurring because of ongoing response to the end of the ice age or other changes inland of or beneath PIG.

We present radio-echo sounding (RES), global positioning system (GPS), and active-source seismic data across the central portion of the Northeast Greenland Ice Stream (NEGIS). NEGIS widens downglacier from a small region of high geothermal flux near the ice divide. Our data reveal high-porosity (40+%) water-saturated till lubricating the ice stream. Ice accelerates and thins as it flows into NEGIS, producing marginal troughs in surface topography. These troughs create steep gradients in the subglacial hydropotential that generate parallel “sticky” and “slippery” bands beneath the shear margins. The low-porosity “sticky” sediment bands limit ice entrainment across the margins and thus restrict further widening, producing the long, narrow, and relatively stable ice stream. However, the observed relations among surface elevation, basal water routing, broad sedimentary drape, and till dilatancy suggest that rapid shifts in ice dynamics are possible, including rapid transmission of ocean forcing inland. The source and routing of the subglacial till are unclear, but our data help constrain hypotheses.

We analyze the internal stratigraphy in radio-echo sounding data of the northeast Greenland ice stream to infer past and present ice dynamics. In the upper reaches of the ice stream, we propose that shear-margin steady-state folds in internal reflecting horizons (IRHs) form due to the influence of ice flow over spatially varying basal lubrication. IRHs are generally lower in the ice stream than outside, likely because of greater basal melting in the ice stream from enhanced geothermal flux and heat of sliding. Strain-rate modeling of IRHs deposited during the Holocene indicates no recent major changes in ice-stream vigor or extent in this region. Downstream of our survey, IRHs are disrupted as the ice flows into a prominent overdeepening. When combined with additional data from other studies, these data suggest that upstream portions of the ice stream are controlled by variations in basal lubrication whereas downstream portions are confined by basal topography.

The article of record as published may be found at http://dx.doi.org/10.1126/science.1239373 Ice shelves play a key role in the mass balance of the Antarctic ice sheets by buttressing their seawardflowing outlet glaciers; however, they are exposed to the underlying ocean and may weaken if ocean thermal forcing increases. An expedition to the ice shelf of the remote Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet that has rapidly thinned and accelerated in recent decades, has been completed. Observations from geophysical surveys and long-term oceanographic instruments deployed down bore holes into the ocean cavity reveal a buoyancy-driven boundary layer within a basal channel that melts the channel apex by 0.06 meter per day, with near-zero melt rates along the flanks of the channel. A complex pattern of such channels is visible throughout the Pine Island Glacier shelf. NSF’s Office of Polar Programs NSF grant ANT-0732926 NASA’s Cryospheric Sciences Program New York University Abhu Dabi grant 1204 Natural Environment Research Council–British Antarctic Survey NSF’s Office of Polar Programs NSF grant ANT-0732926 New York University Abhu Dabi grant 1204

Amplitude analysis of reflection seismic data reveals the presence of highly variable bed conditions under the main sticky spot and adjacent regions of the Kamb Ice Stream (KIS—formerly ice stream C). The sticky spot, which is a zone of bed that imparts high basal resistance to ice flow, is situated on a local topographic high composed of consolidated sediments or sedimentary rock. Any meltwater draining from upglacier along the base of the ice is routed around the sticky spot. The ice over the sticky spot includes, in at least some places, a seismically detectable basal layer containing a low concentration of debris, which locally thickens to 40 m over a topographic low in the bed. The ice-contact basal material ranges from dilated and highly porous to more-compacted and stiff, and perhaps locally frozen. The softer material is preferentially in topographic lows, but there is not a one-to-one correspondence between basal character and basal topography. We speculate that the 40-m-thick frozen-on debris layer formed by glaciohydraulic supercooling of lake-drainage events along a basal channel during the former, active phase of the ice stream. We also speculate that loss of lubricating water, perhaps from piracy upstream, contributed to the slowdown of the ice stream, with drag from the sticky spot playing an important role, and with the basal heterogeneity greatly increasing after the slowdown of the ice stream.

Active seismic imaging of glaciers and ice sheets is important for constraining inputs to climate models, such as englacial ice fabric and the nature of the basal interface. However, acquiring high-quality seismic data is time-consuming and resource-intensive. Using traditional single-element geophones requires ideal weather conditions (e.g. light winds) and excellent source coupling. In addition, deploying and retrieving these geophones is slow and cumbersome. We have developed a four-element ‘georod’ that enhances signal levels by 20–30dB in a variety of conditions, including blowing snow and poorly coupled source detonations. The long, slender design of these georods makes them easy to deploy and retrieve, allowing researchers to acquire greater line-kilometers of seismic data during field campaigns that are commonly time-constrained.

Abrupt changes in crystal-orientation fabric (COF), and therefore viscosity, are observed near the base of the ice sheet throughout West Antarctica. We report on active-source seismic observations from WAIS Divide, mid-stream and downstream on Thwaites Glacier, and the onset region of Bindschadler Ice Stream. These data reveal a prevalence of englacial seismic reflectivity in the bottom quarter of the ice sheet. The observed seismic reflectivity is complex but largely bed-conformable, with long-spatial-wavelength features observed in the flow direction and short-wavelength features observed across flow. A correspondence of englacial structures with bed features is also observed. We determine the origin of the reflectivity to be abrupt changes in the COF of ice, based on the following: (1) observations of englacial reflectivity are consistent with current knowledge of COF within ice sheets, (2) englacial reflectivity caused by COF contrasts requires the simplest genesis, especially at ice divides, and (3) amplitude analysis shows that the observed englacial reflectivity can be explained by contrasts in seismic velocity due to COF changes. We note that the downstream increase in the quantity and complexity of observations indicates that direct observations of COF at ice divides likely underestimate the role that fabric plays in ice-sheet dynamics.

We present a 3-D P-wave velocity model of the combined subaerial and submarine portions of the southeastern part of the Island of Hawaii, based on first-arrival seismic tomography of marine airgun shots recorded by the onland seismic network. Our model shows that high-velocity materials (6.5–7.0 km/s) lie beneath Kilauea's summit, Koae fault zone, and the upper Southwest Rift Zone (SWRZ) and upper and middle East Rift Zone (ERZ), indicative of magma cumulates within the volcanic edifice. A separate high-velocity body of 6.5–6.9 km/s within Kilauea's lower ERZ and upper Puna Ridge suggests a distinct body of magma cumulates, possibly connected to the summit magma cumulates at depth. The two cumulate bodies within Kilauea's ERZ may have undergone separate ductile flow seaward, influencing the submarine morphology of Kilauea's south flank. Low velocities (5.0–6.3 km/s) seaward of Kilauea's Hilina fault zone, and along Mauna Loa's seaward facing Kao'iki fault zone, are attributed to thick piles of volcaniclastic sediments deposited on the submarine flanks. Loihi seamount shows high-velocity anomalies beneath the summit and along the rift zones, similar to the interpreted magma cumulates below Mauna Loa and Kilauea volcanoes, and a low-velocity anomaly beneath the oceanic crust, probably indicative of melt within the upper mantle. Around Kilauea's submarine flank, a high-velocity anomaly beneath the outer bench suggests the presence of an ancient seamount that may obstruct outward spreading of the flank. Mauna Loa's southeast flank is also marked by a large, anomalously high-velocity feature (7.0–7.4 km/s), interpreted to define an inactive, buried volcanic rift zone, which might provide a new explanation for the westward migration of Mauna Loa's current SWRZ and the growth of Kilauea's SWRZ.

Selective cloning of the cDNA coding for a weak neurotoxin (WTX) from cobra N. kaouthia including the 5'- and 3'-non-translated regions (NTR) is described. The known amino acid sequence of WTX was used together with the nucleotide sequence of a weak neurotoxin NNAM2 from cobra Naja atra, to design WTX-specific primers for direct amplification of an internal WTX cDNA fragment by RT- PCR. The sequence of the complete WTX cDNA was determined in sequencing runs on internal PCR products, cloned 3'- and 5'-RACE-fragments and several full-length cDNA clones. The cDNA coding sequence is in excellent agreement with the previously determined WTX amino acid sequence, has a high homology with other known weak toxin cDNAs, whereas even higher homology (up to 96%) with several classes of 3-finger toxins was detected in the 59 bp 3'-NTR consensus sequence. A possible function of the highly conserved nucleotide sequence elements is discussed.

Using 6mer and 12mer phage peptide libraries three unique phage clones were identified which specifically bind to a monoclonal anti-FITC antibody, B13-DE1. The two 6mer and one 12mer peptide insert sequences are clearly related to each other and contain a high proportion of hydrophobic amino acids. The peptides are bound by the antibody combining site of B13-DE1 probably in a similar manner to FITC and represent therefore true peptidic mimics of the fluorescein hapten. No reactivity of the peptides could be demonstrated with another monoclonal anti-fluorescein antibody or with polyclonal anti-fluorescein antibodies. Immunization of mice with the peptides resulted in the production of antibodies cross-reacting with all peptides but not with fluorescein. The results show that phage peptide libraries can be used to isolate mimotope peptides which can mimic low molecular weight structures seen by a specific antibody and probably other recognition molecules. Copyright © 1999 John Wiley & Sons, Ltd.

[1] Seismic attenuation α, or internal friction Q−1, in glacial ice is highly sensitive to temperature, particularly near the melting point. Here we detail a technique to estimate Q and apply it to active source seismic data from Jakobshavn Isbrae, Greenland. We compare our results to measured and modeled temperature profiles of the ice in the region. We find an excellent match, with differences between seismically estimated and modeled temperatures of less than 2°C. Mapping variations in seismic Q through glacial ice thus is shown to allow detailed estimation of englacial temperature profiles, which may be of special value in regions where in situ measurements are logistically difficult.

[1] Seismic reflection data are analyzed to verify radar identification of a subglaical lake near the geographic South Pole. The seismic amplitude variation with offset (AVO) technique is applied to confirm the presence of extensive free water, and seismic imaging of the subsurface constrains lake depth and deeper subglacial structure in the region. This lake is at least 4.2 km wide (and likely as much as 10 km in diameter), is up to 32 ± 10 m deep, and occupies a basin of thick sedimentary strata. These results imply that extensive water storage is occurring in the South Pole region. The proximity of this lake to the Amundsen - Scott South Pole Station makes research drilling to sample the lake and underlying sediments feasible and supportable.

This is the published version. Copyright 2008 American Geophysical Union. All Rights Reserved.

We present the results of a seismic reflection experiment performed transverse to flow a few tens of kilometers above the main trunk of Kamb Ice Stream, West Antarctica, where we image a basal high surrounded by variable subglacial conditions. This high rises as much as 200 m above the surrounding bed, acting as a major sticking point that resists fast flow. Application of the amplitude variation with offset (AVO) seismic technique has highlighted regions of frozen sediments along our profile, suggesting that the ice stream is experiencing basal freeze-on in the region. The bedrock high appears to be at least partially draped in sediment cover, with a concentrated area of weak, dilatant till flanking one edge. This dilatant till is further dispersed along our profile, though it does not possess enough continuity to maintain streaming ice conditions. These results support the hypothesis that the ongoing shutdown of Kamb Ice Stream is due to a loss in continuous basal lubrication. Citation: Peters, L.E., and S. Anandakrishnan (2007), Subglacial conditions at a sticky spot along Ka mb Ice Stream, West Antarctica, in Antarctica: A Keystone in a Changing World - Online Proceedings of the 10 th

Laterally continuous subglacial sediments are a necessary component for ice streaming in the modern onset regions of the ice streams draining the Siple Coast of West Antarctica on the basis of new seismic data combined with previous results. We present geophysical results from seismic reflection and refraction experiments in the upper reaches of ice streams C and D that highlight continuous sedimentary basins within and upstream of the current onset regions of both ice streams, with streaming ice overlying these sedimentary packages. The subglacial environment changes from no-sediment to discontinuous-sediment to continuous-sediment cover along a longitudinal profile from the ice sheet to tributary C1B. Along this same profile, we observe a speedup of ice flow and then full development of the ice stream tributary. Ice stream D flows above a thick sedimentary package with an uppermost low-seismic-velocity zone indicative of soft till, and the upglacier and lateral extensions of ice stream D are tightly constrained by the extent of continuous sediments. The inland termination of these sediments suggests that future migration of high-velocity, low-shear-stress ice flow in these regions appears unlikely.

[1] Earlier observations indicated that Whillans Ice Stream slowed from 1973 to 1997. We collected new GPS observations of the ice stream's speed in 2003 and 2004. These data show that the ice stream is continuing to decelerate at rates of about 0.6%/yr2, with faster rates near the grounding line. Our data also indicate that the deceleration extends over the full width of the ice plain. Extrapolation of the deceleration trend suggests the ice stream could stagnate sometime between the middle of the 21st and 22nd Centuries.

A retrospective study was done to determine the correlation between the rate of aseptic loosening and the early radiographic appearance of the bone-cement interface of the acetabulum of primary cemented total hip prostheses. Two hundred thirty-six hips implanted with modern cement technique were studied during an average clinical and radiographic followup of 9 years. Early radiographs and the last available radiographs were studied by 3 independent observers, and the quality of the bone-cement interface was evaluated with a standardized scoring system. On the acetabular side, the authors noted 0.8% clinical failure, a 3% rate of radiographic migration, and a 3.4% rate of progressive global radiolucency. Only 2.2% of hips considered well fixed on the postoperative film were loose. Of the hips considered not well fixed, the rate of aseptic loosening was 14.4%. The authors conclude that (1) the state of the bone-cement interface as seen on the early postoperative radiograph can predict the longevity of a cemented socket with a high degree of probability, and that (2) cementation of an all-polyethylene socket using modern cement technique is an excellent method of fixation for patients 60 years of age and older with degenerative joint disease.

Life stages of Proterometra autraini n. sp. (Digenea: Azygiidae) from the Au Train River, Au Train, Michigan are described, with emphasis on the cercarial stage. Progenetic cercariae develop in rediae in the snail Elimia livescens and emerge seasonally from mid-summer to mid-autumn. Cercariae emerge naturally between 1000 and 2100 hr EDT. Adults were retrieved from several naturally infected fish species. Specimens of Cottus bairdi (n = 16) displayed the greatest prevalence (75%), mean intensity (7.1), and abundance (5.3) of infection. Experimental infections were successful in C. bairdi, Lepomis macrochirus, and Perca flavescens. The geographical range of this parasite is limited to the portion of the Au Train River between Au Train Lake and Lake Superior.

WITHIN recent years the domestic bird has been used to an increasing extent in physiologic and endocrinologic studies. Some of these investigations have revealed inherent differences between the bird and the mammal (Jailer and Boas, 1950; Zarrow and Baldini, 1952; Morris, 1953; Newcomer, 1959; Nalbandov, 1953). Recently the advent of many new steroids has led to extensive studies on these compounds in the mammal but little work has been done in the bird. The present investigation is concerned with the effect of some of these compounds in the chick and and is designed to determine whether the differences in the action of these compounds in the chick and rat are of a quantitative or qualitative nature and to determine whether some structure-function relationship can be obtained. MATERIAL AND METHODS The chick oviduct test was carried out on 16-day-old chicks of the White Leghorn strain. All birds were injected intramuscularly for …

This report compares the effectiveness of various compounds with progestogenic activity in a series of tests involving the chick the rat the mouse and the rabbit. The inhibition of oviduct growth stimulation of decidual growth and the Clauberg test were used for measurement of activity of 17-alpha-hydroxyprogesterone 17-alpha-hydroxyprogesterone caproate 11 dehydroprogesterone 17-alpha-ethyl-19-nortestosterone and 17-alpha-ethinyl-19-nortestosterone. In the chick oviduct test 16-day-old female white Leghorns were treated for 7 days and sacrificed on Day 8. The entire genital tract from the infundibulum to the cloaca was included in the oviduct weight. Injection of stilbestrol alone gave a typical sigmoid dose-response curve with a sharp increase in weight from 13 mg % of body weight at .05 mg daily to 1048 mg percent at 1 mg daily. A standard dose of 1 mg a day of stilbestrol was then selected for further experiments. Progesterone produced a marked inhibition of the stilbestrol-stimulated oviduct in the chick particularly when dissolved in oil; all the compounds tested showed some inhibition ability. Adult female Holtzman rats were castrated treated with 1 mg of estrone for 4 days followed by 9 days of progesterone or one of the test compounds. The uterus was exposed on Day 5 of test-drug treatment and 1 mg of histamine dihydrochloride injected into the left horn. A marked deciduoma was apparent with .5 mg progesterone daily. The degree of deciduomatogenesis was evaluated by comparing the percentage of increase of the histamine-treated horn with the other. At .2-2 mg daily progesterone gave a good dose response curve up to 400% increase when suspended in oil. Suspension of the hormone in saline with "Tween 80" decreased activity by 50%. 11-dehydroprogesterone was twice as effective as progesterone. The other compounds gave little or no response even in large doses. In mice similar tests showed the decidual response in the mouse is a more sensitive index of progestone-like activity than in the rat. No significant activity was observed with any of the test compounds except 17-alpha-ethyl-19-norethisterone. The Clauberg test in rabbits gave similar results to previously reported work. 11-dehydroprogesterone was effective at .15 mg twice the activity of progesterone. It had only a third the activity of progesterone in the Hooker-Forbes test. Both the 17-alpha-ethyl-19-nortestosterone and the 17-alpha-ethinyl-19-nortestosterone appeared to be superior to progesterone in Clauberg and chick-oviduct tests; the ethynyl derivative was superior to the ethyl derviative in the chick test; only 11-dehydroprogesterone mirrored all the activities of progesterone and was consistently superior to the hormone.

Is there a matrix A which has the property A2 = C? We began by constructing lower triangular matrices which have this property. Alerted by a colleague to work of Hausdorff, Toeplitz, and others, we investigated various convergence properties of our square roots. We used computer-generated estimates of the first 25 rows of two of the square roots to formulate conjectures which we then proved on the behavior of their entries. We showed that the first of these square roots takes convergent sequences to convergent sequences and that the second does not even take bounded sequences to bounded sequences. For a while we believed that all the square roots of C were lower triangular; eventually, having found no obstruction, we proved that all nonzero infinite matrices have nontriangular square roots. Also, our technique for finding lower triangular square roots of C applies to any infinite lower triangular matrix with all positive entries on the diagonal. Halmos was, of course, interested in finding a square root of C which is also a bounded operator, i.e., one which takes square-convergent series to square-convergent series. J. B. Conway has proved the existence of a well-defined bounded subnormal operator vC by using the Conway-Olin functional calculus [1], [2]. Also, by a theorem of T. Kato [3], C has a bounded accretive square root. The proofs are not constructive, so we do not know a matrix square root which is a bounded subnormal square root. In our investigation, we used only elementary techniques. The computations are complex, but require knowledge only of calculus, linear algebra, binomial coefficients and, above all, the principle of induction. Most of the proofs are inductive; the square roots are iteratively defined; the inductive relationship between binomial coefficients reflected in Pascal's triangle is essential. In this note we present our results without proof, but will gladly supply details upon request.

Nematobothrium texomensis occurs primarily in the gravid ovaries of three species of buffalo fishes. The adult is extremely filamentous, attaining a length of up to 2.5 m. It is almost devoid of muscle tissue, capable of little movement, and presumably absorbs nourishment through the cuticle. All sex organs are tubular. The ventral sucker is poorly developed and not recognizable in most specimens. There is evidence that when fish hosts spawn, pieces of worms containing eggs are discharged. Development outside the host is unknown except that miracidia force-hatched from the operculate eggs are of the didymozoid type. Development of N. texomensis is associated with the reproductive cycle of the host and the worm has never been found in a sexually immature fish. The worms die when the fish spawn or begin to resorb unspawned eggs. Eggs do not hatch in the juices of any snail species indigenous to Lake Texoma. Although some hatched in the gut of Succinea avara, no larvae developed. The first known collection of Nematobothrium texomensis consisted of two species from a buffalo fish Ictiobus bubalus taken from Lake Texoma by Dr. Virgil E. Dowell. The worms were profusely entwined through the lamellae of the ovaries, which were gravid, but considerable portions were free in the lumina of the ovaries and about 10 inches of one worm extended through the genital opening. They were filiform and so delicate that they were broken into many pieces during removal. The length of the combined pieces of the two specimens was approximately 5 m. McIntosh and Self (1955) reported this worm as the first known species of the Didymozoidae from a freshwater fish in the Western Hemisphere. McClelland (1955) reported Nematobothrium labeonis from the orbits of Labeo coubie, L. horie, and L. niloticus from the Nile River, and Yamaguti (1936) reported Philopenna higai from the dorsal fin and orbit of Sarcocheilichthys variegatus in Japan. These Received for publication 12 March 1963. * Present address: Department of Biology, Northern Michigan College, Marquette. t Present address: Department of Biology, Southern University, Baton Rouge, Louisiana. +t Work done at the University of Oklahoma Biological Station under support of Grant E 2849 (CL), National Institutes of Health. are the only species of the family now known to occur in freshwater fishes. Nematobothrium texomensis occurs in three species of buffalo fishes: Ictiobus bubalus, I. cyprinellus, and I. niger. While occasionally associated with mature testes, it is most commonly found in the lumina and lamellae of gravid ovaries. In a few cases, it has been found outside the ovary, between this organ and the peritoneum. Specimens frequently extend from one ovary to the other by way of the genital opening and may occur singly or as multiple infections. No living worms have been found outside the body cavity; the remains of dead specimens found immediately external to the peritoneum provide the only evidence that this parasite is a tissue migrant. DESCRIPTION OF THE ADULT Up to 2.5 m in length, 0.5 mm in diameter. Cuticle delicate and opaque to transparent. Socalled oral sucker nonmuscular and completely enclosed within the cuticle (Figs. 2, 12); pharynx present but nonmuscular (Figs. 2, 13); esophagus extends through approximately one-fourth the body length, surrounded by a single layer of epithelial cells (Figs. 2, 14) and divides into crura which extend to posterior end (Fig. 3). Intermittent clusters of glandular tissue surround esophagus (Fig. 15). Male and female genital pores located on a prominence lateral to oral sucker and closely adjacent to each other (Figs. 2, 12). Male duct nonmuscular (Fig. 14). Testes tubular, one con