ALBERT

Notes: Summary Aethalion reticulatum nymphs and adults were found feeding onPiper umbellatum in Costa Rica. Adult females protected their egg masses by sitting atop the masses and scraping their hind legs along the sides. Two parasitoids,Gonatocerus sp. andPterygogramma sp. were reared from egg masses. Nymphs and adults were regularly tended byCamponotus sericeiventris andCamponotus (Tanaemyrmex) sp.Camponotus sericeiventris tended only during the daylight hours and aggressively protected the hemipterans.Camponotus (Tanaemyrmex) sp. was competitively displaced by the former species.

Notes: Summary Alates and primary reproductives were scarce in field colonies which were found in damp decaying logs and stumps on the forest floor. Colonies counted were found to be relatively small compared with those of higher termites and most were found to be headed by a pair or more of supplementary reproductives. A strong correlation was found between headwidth and the number of larval plate ridges on the right mandible which indicated that inP. adamsoni the basic number of larval instars is seven. Pairs of supplementary reproductives held at constant temperatures of 15°, 20° and 25°C produced brood; brood production was inhibited at 28°C. Although 25°C was more satisfactory for the development of primary colonies, 20°C appeared to be more satisfactory for continued development of colonies.

Notes: Résumé Les sites d'accumulation minérale et purique des Termites sont localisés dans le tissu adipeux, les tubes de Malpighi et l'épiderme. Les cations accumulés sont nombreux: Ca, Mg, K, Mn, Fe, Zn, Na. Leur nature et leur quantité dépendent à la fois de l'espèce, du stade et de la caste. L'intervention directe d'une substance alimentaire dans la bioaccumulation n'est évidente que lorsque la nourriture apporte un élément exceptionnellement abondant. Ainsi, le fer n'est présent que chezCubitermes et seulement dans les castes nourries d'humus (ouvriers, soldats). Dans la caste des ouvriers, il faut aussi insister sur le particularisme desCubitermes qui, contrairement aux autres espèces, accumulent peu. La caste des soldats apparaît, par contre, assez homogène (indice d'accumulation du tissu adipeux élevé; fort stockage malpighien). L'évolution qui conduit aux nymphes et aux ailés représente toujours, dans le cycle d'une espèce, la voie la plus importante du point de vue de la bioaccumulation. Soldats et lignée sexuée deSchedorhinotermes, soldats et nymphes deMicrocerotermes etCubitermes sont nourris par trophallaxie, et le comportement social général caractérisant chacune de ces deux «castes» est uniforme dans les trois espèces. Certaines particularités physiologiques et éthologiques propres aux espèces et aux castes concourent donc à l'établissement des divers aspects de la bioaccumulation minérale et purique.

Notes: Summary Factors affecting local geographic distribution, foraging behavior and activity, forage selection, numbers of foragers per colony, nest spacing and nest structure ofPogonomyrmex rugosus andPogonomyrmex barbatus wer estudied. There were seasonal differences in foraging activity.P. barbatus was more active in early summer and foraged at night whileP. rugosus was more active in mid-summer foraging at night during July. Both species exhibited forage preference for grass seeds but took a variety of other materials. Where both species inhabited the same area they had an index of overlap for forage of 0.7. The colonics of both species were randomly distributed. Colony density was approximately 20 per hectare in areas supporting one or both species. There was no evidence of intraspecific aggression and foraging areas of colonies of the same species overlapped considerably.P. barbatus andP. rugosus avoid competition by habitat selection. Interspecific aggression probably accounts for the lack of overlap in local distribution.

Notes: Zusammenfassung Das Sexualverhalten der Gastameise wurde in Laborvölkern untersucht. Die Weibchen vonFormicoxenus, die in einer kompletten morphologischen Uebergangsreihe von arbeiteringleichen zu geflügelten Vollweibehen vorkommen, zeigen ein «Locksterzel»-Verhalten wie es fürHarpagoxenus sublaevis und andere Sozialparasiten des TribusLeptothoracini beschrieben wurde. Während dieses Verhaltens ist die Gaster angehoben, der Stachel wird ausgestreckt und an seiner Spitze erscheint ein kleiner Sekrettropfen. Die ergatoiden, flügellosen Männchen werden von solchen Weibchen über etwa 15 cm Entfernung angelockt. Sie versuchen nicht nur auf sterzelnde Weibchen aufzureiten, sondern auch auf andere, die in der Arena umherlaufen. Durch zerquetschte Weibchen-Gaster und durch isolierte Giftdrüsen kann bei Mänchen ebenfalls Sexualverhalten ausgelöst werden, jedoch nicht durch andere Drüsen oder Körperteile von Weibchen. Das Pheromon löst auch homosexuelles Verhalten unter den Männchen aus. Das Begattungsverhalten wird beschrieben.

Notes: Summary The connective tissue ofApis appears to have three components: amorphous substances, fine and dense filaments and collagen-like-fibrils. These materials form the various structures comprising the connective tissiue that are: external coast or basement membranes, dense coast, neural lamellae, connective or suspending membranes, hollow strands connecting organs, filaments attaching cells, and amorphous substances cementing cells. The external coast and connective membranes are formed of only amorphous substances. The hollow strands are formed of amorphous substances, thin filaments and collagen. The neural lamellae are formed of amorphous substances and collagen and the dense coast of amorphous substances and thin filaments.

Notes: Summary The glucose levels in homogenates of heneybee brood (5th–16th day of life) and in the jelly of each caste (5th–9th day of life) were determined. The glucose level of workers was, during the majority of days tested, up to twice as high as in queens, the most impressive changes in the glucose level occurred during the 5th–8th days of life, at which time there was a parallel rise in the glucose levels of worker homogenate and of the jelly which serves as their food. No such rise was observed in queen brood homogenate.

Notes: Summary We propose a method that may be used to determine the spatial orientation of the fracture plane developed during hydraulic fracture. In the method, magnetic particles are injected into the crack with the fracturing fluid so as to generate a sheet of magnetized material. Since the magnetization of a body with extreme dimension ratios, such as a crack, exceeds that of an equidimensional body and since this magnetization is sensitive both to orientation and geometry, this could be used to obtain information about the crack. By measuring the vertical and horizontal components of the magnetic field and field gradients at the earth's surface surrounding the injection well with superconducting magnetometers having 10−4 gamma sensitivity and also by measuring field direction within the well itself, it should be possible to calculate the orientation and perhaps infer the approximate geometry of the fracture surface. Experiments on electric field potential operated in conjunction with this experiment could further constrain estimates of shape and orientation.

Notes: Summary The relative detection capability of nine seismological stations situated north of 20°N in India has been studied. The best stations were the WWSSN stations NDI and SHL, followed by CHA, DDI, BOK and BHK. The remaining stations CAL, SEH and TOC are inferior in their detection capability.

Notes: Abstract Based on the average variability of the skewness with respect to the droplet mode radius, a wide set of mean size-distribution models is presented in terms of the modified gamma function for fog and stratified cloud droplets. These models appear appropriate for giving reliable size-distribution curves relative to the various formation stages of the droplet population both in fogs and in stratus and stratocumulus clouds. The corresponding volume extinction coefficient has been computed at various wavelengths from 0.4 to 17 μm using Van de Hulst's (1957) approximation multiplied by Deirmendjian's (1960) correction factors. This set of theoretical extinction data has been compared with experimental extinction measurements performed in atmospheres characterized by a marked thermal inversion for describing the evolutionary features of the water droplet size distribution within the whole ground layer.

Notes: Summary Recently determined gravity anomalies along the NW-SE oriented Swiss Geotraverse from Basel to Bellinzona are used in combination with seismic refraction data to deduce a crustal section across the Swiss Alps. Topographic, Bouguer, free air, isostatic and geological corrections were applied to the data. Geological features considered in the corrections are the Swiss Molasse basin filled with sediments and the Ivrea body of high-density material. The resultant Bouguer anomaly over the Gotthard massif is 130 mgal lower than the Bouguer anomaly at the northern end of the profile near Basel. The Alpine region is associated with negative isostatic anomalies down to −20 mgal. The crustal thickness is found to increase gradually from the northern end of the profile (thicknessH=30 km) towards the Helvetic nappes at the northern margin of the Alps (H=38 km) and more rapidly towards the Gotthard massif (H=50 km) and further south to Biasca down to a depth of 58 km. From Biasca southward the crustal thickness thins quite rapidly to reach a depth of 30 km at the southern end of the profile near Bellinzona. Thus the Alps have a distinct asymmetric crustal root whose maximum thickness is almost twice the average crustal thickness in Central Europe. With the Mohorovičić-discontinuity deduced from seismic observations an average constant density contrast of −0.33 gcm−3 is found between the lower crust and upper mantle underneath the Alps.

Notes: Summary Six Younger Granite localities showing normal and reverse magnetizations in equal proportion have given a Jurassic palaeomagnetic pole position ϕ=62.5°N, Λ=241.6°E; (Fisher's precision parameter (k)=27.8 and α95=13°). Individual palaeopole-positions have also been obtained for a Cretaceous pyroclastic rock and for two Pleistocene basalt flows.

Notes: Summary Body force equivalents can be computed for subsidence of the Po delta in the twentieth century. Their preferred location suggests that not all of the subsidence is caused by pumping of fluids or other processes occurring at shallow depths. Some of the deformation may be due to crustal response to a north-south compressive stress.

Notes: Abstract A theory of deep earthquakes, termed the inclusion collapse theory, is proposed in this paper. In the inclusion theory of crustal (or shallow) earthquakes, faults were shown to terminate within an inclusion zone. This zone represents a region within the brittle portion of the lithospheric plate that contains open cracks (voids) of varying sizes that, to a first order approximation, are uniformly distributed throughout the inclusion zone. When the lithospheric plate containing these faults and their associated inclusions is subducted into the mantle, the stress normal to the fault planes must increase. A depth is eventually reached where slippage along the fault planes is no longer possible. Earthquakes are postulated to occur at a specified depth within the mantle as a result of processes leading to collapse of these voids. When the long-term modulus of the plate is much greater than the long-term modulus of the mantle, large pressures are shown to develop within the plate during periods of active subduction. These pressures are shown to be sufficient to initiate partial collapse of voids of similar geometry throughout the inclusion zone. The inclusion collapse theory and the concentration of pressure within the plate lead to four results. (1) Earthquakes that are produced by a void collapse mechanism will not occur below a subduction depth calculated to be between 350 and 1000 km (2) The physical process most likely responsible for producing void collapse is the formation of shear, melt zones whose thicknesses are on the order of 1 to 10 cm in the immediate vicinity of the voids. This mechanism, is shown to produce a ‘precursor’ time on the order of a few hundred seconds during which there is a release of shear strain prior to the earthquake. (3) The maximum energy released by void collapse is independent of the source depth. (4) The number of earthquakes produced by this process will decrease hyperbolically with source depth. Source depth, in the context used in this article, refers to the depth in the mantle to the inclusion zone where voids of similar geometry are undergoing partial collapse. The maximum source depth refers to the depth where all voids have closed.

Notes: Summary Measurements of bulk magnetic properties, including the natural remanent magnetization (NRM), susceptibility and the Königsberger ratio, on over 250 samples of Tertiary basalts from Disko and Nûgssuaq, West Greenland are reported. The NRM intensities in basalts (geometric mean value 3.3 A/m in SI units) were on average three to four times as large as the induced magnetization intensities. The susceptibilities (geometric mean value 2.1×10−2 SI units) were much more uniform than the NRM intensities. In the majority of samples, the NRM was predominantly of reverse (R) polarity, but samples from a few sites showed a remanence of normal (N) polarity. The NRM of both polarity classes (N, R) was very stable against alternating field (AF) demagnetization with median destructive fields of the order of 20,000–30,000 A/m (250–350 Oe), comparable to those for many stable continental and oceanic basalts. The viscous remanence intensity, as studied by storage tests on some specimens, was found to be an insignificant fraction of the original NRM, except in few cases. The low field hysteresis loops (Rayleigh loops) were studied for some specimens. A qualitative association was noted between wide hysteresis loop and relatively low AF stability, but no correlation was apparent between the loop type and the Königsberger ratio (Q n) of a specimen.

Notes: Summary Since 1945 in Poland density measurements have been completed on drilling samples to obtain data for reduction and interpretation of geophysical results. In this paper the developments in density measurements techniques and data processing in Poland are reviewed. Mean density maps have been constructed for the following Pre-Devonian divisions: Volhynian, Valdai and Subholmian Cambrian, Holmian and Protoolenus Cambrian, Middle Cambrian, Lower Ordovician, Middle Ordovician, Upper Ordovician, Lower Silurian, Middle Silurian, Upper Silurian. On the basis of the same data the dependence of mean densities on the present depth of all the above divisions has been examined. This dependence has been approximated by regression equations of the following type: σ(h)= ah + b , σ(h) = ah2 + bh + c, σ(h)= alnh + b(σ(h): mean density,h: present depth). In addition to the coefficients of these equations the correlation coefficient, regression standard error, and confidence intervals have been calculated. Analysis of the results obtained revealed a dominant effect of compaction on the mean density values. Hypotheses have been presented concerning other geological factors responsible for the variation of these values. Regression curves constructed for the individual stratigraphic horizons served to estimate the maximum earlier depth of the Palaeozoic rocks of the Holy Cross Mountains and their vertical displacement. Similar studies have been completed for two adjacent boreholes situated in the Bug River depression. Their results indicate that mean density values can readily serve to estimate the amount of vertical tectonic displacement.

Notes: Summary It is argued that normally the stresses in the lithosphere are hydrostatic or pseudohydrostatic. Several mechanisms are discussed that account for this feature, the more important one being plastic deformation leading to a situation in which the crustal material can be considered as ‘pre-stressed’ inthe horizontal plane. The proposed stress distribution has consequences for crustal model studies, especially when ductile flow is involved.

Notes: Résumé Les roches volcaniques permiennes de la vallée du Guil présentent une ARN de direction voisine du plan de la schistosité alpine qui les affecte. Leur aimantation permienne a probablement été modifiée, lors de l'orogénèse alpine, par les efforts tectoniques (modification d'origine purement mécanique, ou acquisition d'une nouvelle aimantation par effet de pression). L'ARN des roches du Guil ne peut donc pas être prise en référence pour une étude géotectonique de l'arc alpin.

Notes: Abstract A spectral theory of seismic sources is developed which treats earthquake foci as band-pass filters. This concept is applied to focal mechanisms of the type double-couple with moment, and the obtained spectral function of the source is compared with those obtained by other authors. Finally some formulae for the determination of geometric and dynamic source parameters from the ‘bandpass’ parameters are presented.

Notes: Abstract Observations of surface waves depend both on the structure traversed and the nature of the source, and therefore inversion of surface wave data can yield information about both structure and sources. The available methods for structural inversion are compared and discussed and a suggestion made for improved source inversion.

Notes: Abstract The scale invariant inclusion theory of failure is applied to the problem of aftershock sequences. In the inclusion theory, a macrocrack, or void of low aspect ratio, the length of which depends upon the magnitude of the impending mainshock, forms within the inclusion zone of the impending earthquake. The fault zone that precedes the inclusion zone represents that part of the macrocrack that has closed. It is shown that bifurcation (branching) of the macrocrack and its associated fault must occur within the focal region of the inclusion during the growth phase of the earthquake. The bifurcation process produces extensive faulting of the material that comprises the focal region. A prediction of the inclusion theory is that each fault within the focal region will terminate within a zone of concentrated dilatancy that may or may not be in an unstable state. When the zone is unstable, an aftershock will occur. It is shown that these inclusion zones will, on the average, occur near the boundaries of the focal region. Failure of these unstable zones leads to additional failures within the interior portions of the focal region. These failures represent ‘lock point’ failures along the fault(s) and will, in general, exhibit few or no additional aftershocks. The bifurcation model of aftershock sequences leads to five results: (1) The aftershock sequence will exhibit an inverse hyperbolic time decay law when the stresses that are applied at distances far removed from the hypocenter remain constant during the sequence and when there isno interaction between the brittle lithosphere (where aftershocks occur) and the underlying asthenosphere. (2) The mean magnitude of any group of aftershocks within the sequence will be approximately constant in time. (3) The aftershocks will, in general, have focal mechanisms identical to that of the mainshock. (4) Large seismic events that occur throughout the aftershock zone will be independent of one another when the aftershocks are sufficiently far apart (∼two-three ‘fault’ lengths) and when the applied tectonic stresses remain constant during the sequence. (5) The bifurcation model predicts that theb-value of the aftershock sequence will be 1.0 when both the Utsu relationship between aftershock area and mainshock magnitude and the Gutenburg Richter frequency-magnitude relationship are satisfied.

Notes: Summary A detailed description is given of a data analysis procedure for phase velocity determination from long period seismograms.

Notes: Summary Three methods of computing the partial derivatives of dispersion curves are briefly described and compared: numerical differentiation, variational methods and an implicit function method.

Notes: Summary The dispersion of higher modes of surface waves over a region covered by an array of stations can be measured by applying a frequency-wavenumber transform to segments of the signals in these stations, centered at a number of group-velocities. Thus, at a fixed period, modes appear as separate maxima in a display of the power spectrum on a phase-velocity vs. group velocity plane. For regions of mild lateral heterogeneity, the main source of error is shown to be due to the inadequacy of the array-response. Numerical experiments with synthetic signals indicate that a precision of the order of 1% can be obtained with a realistic number of stations. Improvements should be obtained by averaging data obtained from different events. The danger of misidentification of modes can be reduced by iteratively removing the sidelobes from the mode-separation diagram.

Notes: Summary Two different viewpoints of the phase velocities of the elastic surface waves in isotropic, laterally inhomogeneous media have led to inconsistent results. Arguments in terms of surface wave modes give the conclusion that the phase velocity is independent of the propagation direction, while the outcome of calculations based on a constructive interference of body waves in a surface layer is that the phase velocity is dependent on the propagation direction. Both arguments are summarized and an error in the calculations giving dependence is pointed out. The calculations and observations of surface wave amplitude changes in laterally inhomogeneous media are also summarized.

Notes: Abstract Linear trend analysis of geophysical time series is considered in connection with the problem of determining long-period variations (possibly of man-made origin) in the presence of short period noise of larger amplitude. Criteria for testing hypotheses about linear trends are presented for the cases of independent observations and of the observations whose correlation function is known. The possibility of increasing the precision of the results using area-averaged values is investigated. Examples are given of the long time series analysis of air temperature, carbon dioxide and water vapor content. Time series of total atmospheric ozone content at some stations are also considered, and conditions for correct statistical analysis of such data are given.

Notes: Abstract The presence of lateral contrasts of electrical conductivity modifies the original pattern of electromagnetic fields radiated from remote sources. A magnetic transverse plane wave field, interacting with a vertical conductive and outcropping dike placed between two quarter-spaces of unequal electrical conductivities, creates an anomalous vertical component of the magnetic field. This anomalous field has been analysed by computation, and drafting of master curves. Two case histories are presented to illustrate the application and the effectiveness of the solution. It is concluded that: (i) the response is higher for intermediate values of the conducting body induction number; (ii) the curves can be used for the inter-pretation of magnetotelluric, AFMAG, and VLF exploration data; (iii) it is necessary to develop solutions taking into account the vertical as well as the lateral variation of conductivity.

Notes: Summary The microwave emissivity of relatively low-loss media such as snow, ice, frozen ground, and lunar soil is strongly influenced by fine-scale layering and by internal scattering. Radiometric data, however, are commonly interpreted using a model of emission from a homogeneous, dielectric halfspace whose emissivity derives exclusively from dielectric properties. Conclusions based upon these simple interpretations can be erroneous. Examples are presented showing that the emission from fresh or hardpacked snow over either frozen or moist soil is governed dominantly by the size distribution of ice grains in the snowpack. Similarly, the thickness of seasonally frozen soil and the concentration of rock clasts in lunar soil noticeably affect, respectively, the emissivities of northern latitude soils in winter and of the lunar regolith. Petrophysical data accumulated in support of the geophysical interpretation of microwave data must include measurements of not only dielectric properties, but also of geometric factors such as finescale layering and size distributions of grains, inclusions, and voids.

Notes: Summary The results of comparisons of experimental data on the A3 2775 kHz absorption, X-ray (1–8 Å) flux and Lyman-α radiation are compared with model data on ionization-rate and radio-wave absorption height profiles. The Lyman-α radiation is found to dominate even in the upper D-region ionization (except flare conditions). A significant increase of usually used nitric oxide concentrations from rocket airglow measurements is required for achieving the best agreement between experimental and model data.

Notes: Summary An analysis of the characteristics of the eddy diffusivity is made, and the equation for turbulent diffusion in a linear flow is derived. This diffusion equation is solved analytically.

Notes: Summary Internal waves are considered on the hypotheses of small disturbances and the Boussinesq approximation. Consideration is given to the lowest internal mode propagating along athin thermocline, and an approximate calculation is made of the dispersion relation, including an explicit representation of the dominant correction for thermocline thickness. Then, the Stokes drift velocity is calculated (a) approximately for this mode in the thin-thermocline model, and (b) numerically for the first two internal modes associated with a single thick thermocline. Finally, a calculation is made of the mass transport velocity field induced by the interaction between pairs of waves (surface or internal), having thesame frequency but arbitrary directions of propagation.

Notes: Summary The decrease in elastic constants due to dilatancy in the earth's crust may bring about changes of its loading response to ocean tides. The amount of change is estimated by two-dimensional finite element analysis. The results show that if a dilatant zone of thicknessd underneath a coastline extends seaward and under the land, then amplitude changes will be detectable at distances 3d andd inland for strain and tilt tides, respectively. An anisotropic decrease of elastic constants in the vertical direction only will reduce the range by one half at most for strain tides especially.

Notes: Summary The D.C. and A.C. electric conductivity and the dielectric constant of a set of 8 eclogites from the Bohemian Massif is studied under high temperatures (200–900°C) and pressures (up to 20 kb). The electric conductivity of the studied eclogites is strongly affected by the content of symplectite minerals: their conductivity increases with their concentration. The average increase of conductivity with pressure between 1 kb and 20 kb is about 50% and is manifested particularly below 4 kb. The correlation between the electric conductivity and the dielectric constant is very high (r=0.975) and allows for the values of one parameter to be estimated from those of another.

Notes: Abstract A study is presented of a possible correlation between ozone and Aitken nuclei concentration measured between 6 km and 19 km by the instruments installed on the WB-57F aircraft. Samples were taken between 48°N and 9°S latitudes over the U.S., the Gulf of Mexico, and Central and South America between March 1974 and February 1975. A weak negative correlation between AN and ozone concentrations was found at altitudes higher than the tropical tropopause. Scattering of the signs and magnitudes of correlation coefficients was found below the tropopause. Largest variations of the coefficient values were related to the stratospheric pollution following the eruption of the Guatemalan volcano Fuego.

Notes: Summary The various data processing techniques (downward continuation, first and second derivatives and their downward continuation) used in gravity interpretation, are analogous to different types of linear filtering operations whose theoretical filter (amplitude) responses can be derived from $$(u^2 + v^2 )^{N/2} \exp (d\sqrt {u^2 + v^2 } )$$ by suitably choosingN andd, whereu andv are angular frequencies in two perpendicular directions,d the height or depth of continuation in unit of grid interval; andN denotes the order of the vertical derivative. By incorporating a mathematical smoothing function, $$e^{ - \lambda (u^2 + v^2 )} $$ (λ being the smoothing parameter) in the theoretical filter response function, it has been possible, by selecting a suitable value of smoothing parameter, to establish an approximate equivalence of the effect of the mathematical smoothing with the inherent smoothing introduced, because of the numerical approximation (approximation error) for practically all data-processing techniques. This approximate equivalence leads to a generalized method of computing sets of weight coefficients for various data-processing techniques from filter response matching method. Several sets of weight coefficients thus have been computed with different smoothing parameter. The amplitude response curves of the various existing sets of weight coefficients have also been calculated for assessing the quality of the approximation in achieving the desired filtering operation.

Notes: Summary The capacity for autodifferentiation of the endoderm of the digestive tract of the chick embryo and the culture conditions which permit the differentiation of the endoderm in the absence of mesenchyme were studied using the vitelline membrane. 0 1. Endodermal epithelia are unable to develop, when cultured alone directly on the basal medium. 2. However, when cultured enveloped in a fragment of the vitelline membrane according to Wolff's method (1961), the endodermal epithelia taken from various parts of 4- to 9-day digestive tracts survive and differentiate into a specific type of epithelium according to their origin, in the absence of mesenchyme. 3. Similarly, when cultured enveloped in a fragment of the vitelline membrane in the absence of mesenchyme, 2.5-day (stage 14 to 18) endodermal pieces differentiate into several types of histologically identifiable digestive tract epithelia: those of oesophagus, proventriculus, gizzard, pancreas, liver, small intestine, and large intestine. 4. The endodermal epithelia cultured in vitro enveloped in the vitelline membrane undergo the following sequence of events: On the 1st day, the epithelial cells lose their orientation. From the 2nd to the 3rd day, the cells orientate themselves again and form an organized epithelial layer. Then mitoses take place. From the 5th day onward, they start to differentiate. 5. Serum in the basal medium is essential, but embryo extract is dispensable for the autodifferentiation of the endoderm under the present culture conditions. 6. Egg-albumen or vitreous body can substitute for the vitelline membrane and allow survival and differentiation of the endoderm in the absence of mesenchyme. 7. Similar endodermal differentiation is achieved even when the endoderm is cultured enveloped in a fragment of the vitelline membrane which has previously been separated mechanically into two layers or subjected to treatments with heat, 0.1 N HCl, 0.1 N NaOH, ethanol, acetone, or 5.5 M NaNO2.

Notes: Summary Mitomycin C, a known inhibitor of DNA synthesis, was injected into white prepupae ofPhormia regina, Adults which developed from these prepupae showed alterations of the bristle pattern, loss of whole bristle organs, and the formation of bristles without sockets or sockets without bristle shafts. Dose-dependence was found for all modifications. For the abdominal microchaetae, the period of maximum sensitivity to the drug began at 16 h after puparium formation, that is well after all of the macrochaetae and most of the microchaetae of the thorax and the head had grown insensitive. Bristle forming trichogen and tormogen cells developed high degrees of polyteny with distinctly banded chromosomes. Photometric determination of the amount of Feulgen-DNA per nucleus led to estimations of DNA classes ranging from 256C to 2048 C. DNA contents of nuclei from Mitomycin C treated animals were significantly lower during the actual growth of the bristle apparatus, but reached approximately the same level as the controls prior to the time of emergence. Cytological investigations proved that doses of Mitomycin C which yielded bristle organs either without sockets or without shafts do not affect the differential division of the bristle mother cell. Polytene chromosomes damaged by Mitomycin C displayed a diffuse and irregular banding pattern. Possible modes of action of Mitomycin C on replicating polytene chromosomes are discussed.

Notes: Summary Ultrastructural observations were made on imaginal leg discs ofDrosophila cultured in vitro in Mandaron's medium M in the presence of α- or β-ecdysone. During evagination of discs in vitro the tight epidermal folds of the disc flatten out progressively and the cells change their shape. As the discs evaginate, the pupal cuticle is secreted at the apex of the cells: it comprises a three-layered cuticulin, an epicuticle and a thick endocuticle. Secretion of pupal cuticle always starts by the appearance of dense deposits at the apex of microvilli. Only the latter apparently participate in the construction of the three successive layers of the pupal cuticle. During disc development an abundant rough endoplasmic reticulum is formed. Nuclei and nucleoli become progressively enlarged. At the same time, the nucleus, initially located near the base of the cell, moves closer to the apical cell surface. Microtubules become fragmented as soon as evagination begins and are reorientated parallel to the cell surface (i.e. parallel to the new long axis of the cell) at the end of evagination.

Notes: Summary Time-lapse photomicrographs of eggs from the Ichneumonid waspPimpla and from the gall midgeWachtliella reveal that during fixation the ooplasm performs excessive streaming movements when conventional fluids such as Bouin's or Dubosq-Brasil's are used. InWachtliella, intravitelline cleavage may continue for two mitotic cycles during fixation. The cytoplasm of individual egg regions may become displaced up to 45% of the egg's length inPimpla, and up to 14% of the egg's length inWachtliella. Therefore fixed preparations may grossly misrepresent the distribution of egg components in the living state. The changes can be traced back by microkymographic registration of movements during fixation. Microkymograms for this purpose were obtained by projecting a time-lapse film through a slit onto photosensitive material mounted on a rotating drum. The shifting of egg components and the mitotic activity of nuclei fail to occur when the egg is treated with a buffered solution of OsO4 (1%, 1 min). Subsequent fixation with glutaraldehyde results in satisfactory preservation of microtubules.

Notes: Summary A carrier protein fraction (CPF) from larval haemolymph was found to influence binding and catabolism of tritiated juvenile hormone (JH) in homogenates of larval epidermis. The CPF reduced binding of tritiated JH in all of the particulate fractions but did not alter the relative binding pattern when compared with JH alone. The CPF also protected the hormone from degradative enzymes in the membrane vesicle and microsomal + cytosol fractions but not in the nuclear and mitochondrial fractions. Preliminary evidence exists for high-affinity binding sites for JH in the nuclear and mitochondrial fractions. We conclude that the CPF influences catabolism of the tritiated JH but does not participate in subcellular recognition of JH in homogenized target tissue.

Notes: Summary Epidermal wound healing in regeneratingDugesia tigrina (Planaria) has been studied using scanning electron microscopy (SEM). The normal epidermal surface and its differentiations have been descrebed. Observations on living material reveal the highly dynamic state of the wound in invididual animals and its more or less continously changing size due to the state of activity of the animals. These observations show good agreement with the SEM studies, which allow a clear delineation of cellular details of the wound, the wound margins and the apposing epidermal regions. These details are described. The over-all picture of planarian wound healing that emerges is briefly as follows: Epithelization is characterized by absence of proliferation from the “old” intact epidermis. Variable contraction of smooth muscle cells reduces the wound size to a certain extent. Simultaneously with this and also during a longer period epidermal cells adjacent to the wound are extending and some become highly attenuated. These two processes together are only to a certain degree effective in wound closure because of a definite epidermal cell deficit which is reflected in the emergence of an epidermal wound edge reflecting the maximal contribution of these two processes to an attempt to close the wound. Complete epithelization is effected by the operation of a third mechanism: Recruitment of cell through flow of subjacent “blastemal cells” (including rhabdite-forming cells) along the wound border; these cells subsequently occupy a peripheral position in the wound. This process is supplemented by cell immigration and insertion into the adjacent old epidermis and in the wound cell sheet. Rhabdite-forming cells contribute predominantly to this process. Eventually integration between old epidermal cells and the newly recruited cells which differentiate into epidermal cells results in final epithelization. Complete wound healing is based on interactions between the epidermal cell system and the regenerating subepidermal membrane-connective tissue filament-muscle cell system.

Notes: Summary Cell lineage relationships observable inDrosophila gynandromorphs have been used to locate the primordia of the individual thoracic disc relative to each other in the embryo. Three observations indicate that the borders of the individual disc primordia lie very close to each other, separated by few if any non-disc cells.First, the frequency of mosaicism within each disc indicates large primordia, of similar magnitude to the distances between the centres of adjacent primordia.Second, very few XX/XO-borders cut between adjacent discs without also cutting into one or the other disc.Third, sturt distances between points on adjacent discs are often much smaller than distances measured within individual discs. The proximity of disc primordia suggests that the individual discs might share common precursor cells in the early embryo.

Notes: Summary The effect of suboptimal levels of α-ecdysone on the differentiation in vitro ofDrosophila melanogaster wing discs was enhanced by the addition of larval fat body to the cultures. However, similar experiments with β-ecdysome showed no enhancement. It is suggested that a partial conversion of α-ecdysone to β-ecdysone by the fat body may well account for these results.

Notes: Summary Non-histone chromosomal proteins (NHCP) were injected into the blastocoel of advanced blastulae fromPleurodeles waltlii which were previously punctured. NHCP extracted from the liver of the same amphibian species bring very strongly inhibitory effects on morphogenesis: gastrulation is prevented in 75% of cases, but the embryos can survive for 8 to 10 days without showing any necrotic cells, and cell divisions still occur sporadically. Intercellular adhesivity is strongly impaired in such embryos, in connection with inhibition of morphogenetic movements. Gastrulation is delayed and abnormal in other embryos, and neurulation is severely disturbed, the neural tube being unclosed or much reduced in size and the notochord and somites poorly differentiated. In contrast, NHCP extracted from other animal species (rat and chicken liver, rat ascites) have practically no effects onPleurodeles embryos. Species-specific inhibitory effects are thus demonstrated and compared with those which were previously studied on cultures of differentiating embryonic cells fromPleurodeles waltlii andAmbystoma mexicanum. The possible levels at which NHCP act are discussed, the changes in intercellular adhesivity being noted as more conspicuous in the present experiments.

Notes: Summary Testes of the early and middle third larval instar ofD. hydei were cultured for a period of 1 to 8 weeks in adult hosts of both sexes. During the culture period spermatogonia and primary spermatocytes passed through the meiotic divisions and differentiated into late elongated spermatids. The latter could be observed with still normal ultrastructure, but also in different stages of degeneration. Autoradiographic studies revealed a normal time course of spermatogenesis during the first week of culture in the adult host; further culture led to a retardation in development. Measurements of the teste's length and autoradiographic labelling showed that the gonads grew only slightly while cultured in the adult host. The size of the testes and their spermatogenic activity are correlated such that the number of postmeiotic germ cell cysts increases with the volume of the gonad. Spermatogenesis is more intensive in tested which were cultured in females than in those cultured in males, and is also favoured in metamorphosing hosts as compared to adult flies. Optimal nutritive conditions of the host flies evoked an increase in the testis' length and number of postmeiotic cysts formed, compared to those which were simply reared on standard food. The addition of exogneous β-ecdysone stimulated spermatogenesis and somatic growth, especially at suboptimal nutritive conditions. It is suggested that both nutritive conditions and the level of ecdysone play a role in gonadal development.

Notes: Summary Non-ribosome-bound 9S RNA was prepared from cytoplasmic ribonucleoprotein of erythropoietic and non-erythropoietic tissues. The RNA was assayed for Hb-mRNA content in a cell-free protein synthesizing system. Free Hb-mRNA was found in the cytoplasm of chick erythroblasts but not in chick embryo brain cytoplasm.

Notes: Summary 1. Umbrellar fragments of the leptomedusaCampanularia johnstoni with or without parts of the radial canal demonstrate a gradient in the potential for manubrium regeneration and in regeneration time. 2. Implantation experiments exclude the manubrium as a source of inhibition or induction in the regeneration of another manubrium. One special case of inhibition appears to be due to competition for a common substrate. 3. Medusa fragments consisting of only peripheral umbrella (C-fragments) undergo a considerably different restitution process as compared with fragments including a central portion of the umbrella (A-fragments). Vital stain is seen to disperse in the subumbrellar tissues during this process in C-fragments, whereas vital stain in A-fragments is observed to accumulate and later on is incorporated into the regenerating manubrium. 4. The mesogloea of different-sized A-fragments retains a stable form when freed of its adhering cellular components, after a 12–24 h regeneration period; for C-fragments, however, the same result is not observed until 72 to 96 h after their excision. 5. InPodocoryne carnea the observed gradients in manubrium regeneration can be abolished when the subumbrellar tissues are separated from the mesogloea by collagenase treatment. 6. A model for manubrium regeneration in interradial fragments, based on the influence of tension exerted by the cicatrization process and the counteracting mesogloeal force, is presented and discussed.

Notes: Summary UsingTriturus pyrrhogaster embryos, the effects of uninduced cells on the differentiation of induced cells were investigated. The inducing stimulus was given to the presumptive ectoderm of early gastrulae by treatment with protein sooution from guinea pig bone-marrow. Mesodermal induction was evoked in the ectodermal explants. After the treatment, some of the ectodermal explants were cut into pieces 1/8 of their original size and combined with untreated presumptive ectoderm. Mesodermal tissues were differentiated in the combined explants too, but the mesodermal tissues evoked in these combined ectodermal explants were different in their regional characters from these in uncombined explants; dorsal structures, such as notochrod and muscle, were observed predominatly in the latter, whereas the dominant structures observed in the former were ventral ones, such as mesothelium and mesenchyme. The shifting of the regional characters in the combined explants was regarded as the result of an unknown effect from the uninduced cells.

Notes: Summary A temperature-sensitive cell autonomous mutation ofDrosophila, l(1)ts-1126 (1–16±2), that affects the rate of cell division is described. When mutant animals are exposed to the restrictive temperature of 29°C during the first and second larval stages, the growth rate of the larvae is retarded. A delay in pupariation occurs during which larvae reach their full size, and the resulting flies are normal. When mutant animals are exposed to restrictive temperature during the third larval stage, growth is also retarded but no delay in pupariation occurs, and the resulting flies are reduced in size. Their small size is due in part to a decreased number of cells and in part to a smaller size of the cells. X-ray induced, marked, homozygousl(1)ts-1126 clones in an otherwise normal animal, are smaller in animals exposed to pulses of restrictive temperature when compared to clones in animals kept at permissive temperature of 22°C. Clone size decreases as pulse length increases. Clones on the wing blade induced 24 h after oviposition are smaller than clones induced at 48 h in animals grown at restrictive temperature. This result is interpreted as an inability of the slower dividingl(1)ts-1126 cells to survive when in competition with wildtype cells. The distribution of survivingl(1)ts-1126 clones in gynandromorphs grown at restrictive temperature supports this conclusion.

Notes: Summary The posterior pole cytoplasm of early embryos ofDrosophila melanogaster was irradiated with increasing doses of U.V. light at a wave length specific for nucleic acids 35 and 75 min after ovoposition, when nuclei were still inside the yolk mass. Probit analysis showed that: Sterility was higher in irradiations performed at 35 min. Mortality was higher in the experiment performed at 75 min. After treatment at 35 min, sterility and mortality were independent phenomena. The numbers of targets involved in germ cell determination were of the order of tens and hundreds at 35 and 75 min respectively. The numbers of targets involved in viability were of several orders of magnitude in both developmental stages. The irradiation, even at very low doses, caused a background effect which was probably due to “old” embryos. The sex ratio was distorted in favour of females at high doses and of males at low doses.

Notes: Summary Salivary glands of 9–10 day oldlethal giant larvae (l(2)gl, 2–0.0) respond to culture with ecdysone in a similar manner to mid third instar glands from wild type larvae. In particular, the ecdysone dependent puffs characteristic of pupariation, not previously observed in this mutant, are immediately induced. The secretion of the stored ‘glue’ granules into the lumen of the salivary glands is also induced by ecdysone inl(2)gl.

Notes: Summary Gynandromorphs with female XX-and male XO-areas result from the loss of an unstable ring-X-chromosome in the early cleavage mitoses of ring/rod-X-chromosome heterozygotes. The phenotypes of the recessive alleles on the rod-X-chromosome are expressed in the XO-areas. 377 larval gynandromorphs of the genotypeR(1)2, In(1)w vC /y w sn3Iz50e mal were examined and scored for the phenotypes of 13 paired and 10 unpaired structures (Table 2, Fig. 2). This was possible mainly by the cell-autonomous expression of aldehyde oxidase activity in soft tissues and by the comparison of the distribution of enzyme activity in wildtype and gynander larvae. The distances between pairs of structures were calculated in sturt-units (Tables 3 and 4). A morphogenetic fate map with the presumptive areas of larval structures was constructed (Fig. 3). The relative positions of the structures agree well with Poulson's fate map (Fig. 4). In addition, the distribution of phenotypes was scored in 380 adult gynandromorphs Table (5). The fate map (Fig. 5) which was constructed from these data is very similar to the fate map of larval structures. This similarity becomes even more pronounced if fate maps are constructed which contain only structures analogous in larva and imago (Table 6, Fig. 6). Therefore an attempt was made to set up an integrated morphogenetic fate map containing the presumptive areas of both larval and imaginal structures (Fig. 7). The possibilities of further blastoderm mapping are discussed.

Notes: Summary The first haemopoietic centres in the embryo ofPterophyllum scalare are found in the blood islands of the yolk sac. These results are in contrast to the classical theory of blood formation in teleosts, which maintains that the first blood formation occurs intraembryonically, in the so-called intermediate cell mass of Oellacher. InPterophyllum, the intermediate cell mass forms only the axial blood vessels. Haemopoiesis in the post-embryo is carried out by the pronephros. This organ remains haemopoietic to the adult stage. In the adult, the pronephric tubules are degenerated; the organ is filled with haemopoietic tissue and also contains strands of adrenal tissue. The adult kidney (mesonephros) is also haemopoietic, though to a much lesser degree than the pronephros. The blood islands in the yolk sac form only stem cells (haemocytoblasts) and proerythroblasts. Released into the circulation, they differentiate and mature into round, disc-like erythrocytes (erythrocytes-E). Erythropoiesis in the pronephros produces elliptical erythrocytes (erythrocytes-ImA). Thus for the latter part of the postembryonic phase, until complete absorption of the yolk, there is a mixed erythrocyte population in circulation. During metamorphosis into the laterally-compressed adult, the adult type of erythrocyte (erythrocyte-A) makes its first appearance. Leucocytes and thrombocytes appear much later in development than the red blood cells. They are formed in the pronephros and are seen in circulation only after the yolk has been absorbed.

Notes: Summary The absolute durations in minutes of the periods from insemination till the onset of gastrulation, the end of epiboly and appearance of the 10th pair of somites, as well as the intervals between these stages, have been determined in 7 species of Teleostei. Their relative duration, in terms of mitotic cycle time units {ie313-1} has also been determined. The biological age (expressed in number of {ie313-2} units) at which the isolated blastoderm becomes capable of differentiating in vitro was also determined in 4 of the species. The relative duration of the periods studied in all the species was shown to be stable at optimal temperatures. The corresponding periods of development have similar duration in closely related teleost species (i.e. belonging to the same genus). The relative duration of the cleavage period varies among the species belonging to different families. These variations are correlated with differences in the amount of yolk in the egg and the degree of psychrophily of the species compared. By contrast, the relative duration of the period between the onset of gastrulation and the stage of 10 pairs of somites was found to be very similar in species which belong to different orders and differ with respect to the amount of yolk in the egg and the temperature ranges of development. The rate of movement of blastoderm cells during epiboly is higher, the larger the eggs in the species under study. The variations in the age at which the isolated blastoderm acquires the ability to differentiate in vitro are not always correlated with the amount of yolk in the egg. The hypothesis is proposed that an interaction between the yolk and active cytoplasm, which determines time of the onset of ribosomal RNA synthesis, is of importance in controlling the temporal relationships in early embryogenesis.

Notes: Summary A monster embryo with a head on each end developed from an abnormalDrosophila egg produced by a M(1)oSp/Binsn female. The embryo probably represents a longitudinal mirror duplication of head and all 3 thoracic segments. The significance of this type of pattern anomaly for embryonic pattern specification inDrosophila is discussed.

Notes: Summary The development of muscle proteins in the thorax of the meal mothEphestia kühniella Z. was studied during metamorphosis and imaginal development by immunological methods. The antigens of the thorax muscle proteins are identical in the last larval instar and in the imago. After the breakdown of larval thoracic muscles (24 h after pupal molt) no muscle antigens are detected. Just before the indirect flight muscles are striated, 4 antigens of imaginal thoracic proteins reappear sequentially. An antigen which in not found in larval or imago muscle occurred between the pupal molt and muscle striation. The immuno-chemical results are correlated with morphological findings. They indicate a resynthesis of contractile proteins in the thorax during metamorphosis.

Notes: Summary Genetic eye mosaics ofDrosophila melanogaster have been studied by means of anatomical techniques. Using different cell markers it was found that the ommatidia at the boundaries between phenotypes are composed of cells belonging to different clones. Therefore, the formation of an individual ommatidium does not obey a mechanism based on a common clonal origin of its constituent elements. A statistical analysis of mosaic ommatidia shows that there is a significant tendency for the receptor cellsR2-R5 on the one hand and the receptor cellsR1, R6 andR7 on the other to belong to the same cell clone. The implications of these findings are discussed.

Notes: Summary The rate of the first four cleavage divisions has been investigated in 8 teleost species. A comparison of cytological studies of the duration of the mitotic cycle in four species with visual observations on the intervals between the appearance of furrows of the first four cleavage divisions in the same species at the same temperatures has shown that in teleosts the duration of the mitotic cycle during synchronous cleavage divisions ({ie301-1} equals one half of the time period between the appearance of furrows of the 2nd and 4th cleavage divisions. At optimal temperatures, it also corresponds to 1/5 of the period between insemination and the appearance of the 1st cleavage furrow. Using these two method, {ie301-2} values were calculated in the species under study for a wide temperature range and curves of the temperature-dependence of {ie301-3} were constructed. Temperatures below the spawning temperature range produced a shortening of the relative duration (in terms of {ie301-4} units) of the period between insemination and the appearance of the 1st cleavage division furrow, as well as a shift in temporal relationships between the successive mitotic phases: the relative duration of the active mitotic phases (especially metaphase) decreased sharply while the overall relative duration of telo-, inter-and prophase increased correspondingly. On the basis of the results obtained the question of the determination of the lower limit of the optimal temperature range in teleosts is discussed.

Notes: Summary In order to support the demonstration of the regulative capacity of the chick limb bud, already stressed by one of us (Kieny, 1964, 1967), heterospecific combinations were made between chick and quail tissues, the cells of the latter bearing a distinctive nuclear marker. A Japanese quail whole limb bud (stage-18 to 21 of H. H., wing or leg) was grafted distally onto the prospective zeugopod of a chick (stage-22) wing bud sectioned at the prospective wrist level. Thus, from a heterospecific surplus recombinant containing five prospective limb segments (stylopod and zeugopod from the chick host; stylopod, zeugopod and autopod from the quail graft), it was possible to obtain a normally shaped appendage that comprised either upper arm, lower arm and hand in the case of a wing bud graft, or heteromorphic upper arm, lower leg and foot in the case of a hind-limb bud graft. In these cases, regulation for excess appeared to take place mainly within the host tissues. The three proximal segments of the recombinant, namely the chick stylopod and zeugopod of the host's stump and the quail stylopod of the graft, became reorganized and gave rise to a single stylopodial segment, which usually contained a double stylopodial bone element, one of chick, the other of quail origin. The absence of development of the squeezed prospective zeugopod can be interpreted as follows: owing to an interaction with the stylopodial graft tissues, the zeugopodial cells of the juxtaposed stump boundary have shifted proximally their originally more distal positional values, so that they changed their prospective pattern of differentiation to that of stylopod. These reset zeugopodial cells combine with the stylopodial cells of host and graft and form a huge composite stylopod, in which, due to an asynchronous determination in the two species, chick and quail tissues do not cooperate fully for the development of a single bone.

Notes: Summary The development of the rhabdomeric pattern in the compound eye ofDrosophila has been studied using combined transplantation and electron microscope techniques. In a first series of experiments eye imaginal discs of increasing age were implanted into larvae ready to pupate, thus losing variable amounts of the normal time for development. A sequence of differentiative abilities was found in the metamorphosed test pieces. As far as the photoreceptor cells are concerned, the most prominent steps of this sequence are: ability to form groups with other similar elements, anatomical polarization of microvilli, establishment of the rhabdomeric pattern and formation of an equator line. The stability of determination of the equator line was tested in a second experimental series. Fragment of different topographical origin within the mature eye anlage were brought to metamorphosis by implantation into larvae ready to pupate. It was found that an equator line differentiates only in those pieces which according to the published anlage maps contain the prospective equator region prior to metamorphosis. The mitotic abilities of implanted eye imaginal discs were investigated by means of “in vitro”3H-thymidine pulse-labelling and light microscope autoradiography of the differentiated test pieces. During the third larval stage the eye anlage is traversed by two consecutive mitotic waves, each one of them producing different categories of receptor cells. The first, anterior wave predominantly produces cells oriented toward the poles of the eye within the ommatidia, while the second, posterior wave gives rise to elements exclusively in an equatorial position. The dynamics of this proliferation are discussed in relation to the findings in the implantation experiments. Silver-grain counts support the possibility that at least two successive cell divisions occur in the eye anlage between labeling with tritiated thymidine and beginning of morphological differentiation. The relevance of this finding for the understanding of the concept of acquisition of competence is discussed.

Notes: Summary Hydra regenerating heads release at least two substances into the surrounding medium: one stimulates and one inhibits head formation. The inhibitor is released mainly during the first hour after cutting, the activator is released more slowly with a maximum in the second hour and with substantial release still during the following six hours. The release of both substances seems to be specific for head regeneration: it is not found in animals regenerating feet. The sequential release of these substances leads to the early changes observed at the cellular level during head regeneration inhydra: the inhibitor produces a decrease, the activator an increase in the mitotic activity of interstitial and epithelial cells, if assayed on intact animals. Head regeneration is blocked, if the release of the head activator is prevented. It is therefore suggested that these substances are necessary to initiate head regeneration inhydra.

Notes: Summary The process of cortical change upon fertilization of eggs of the teleostean fish,Oryzias latipes was investigated. A cortical alveolus (CA) contains colloidal material, a spherical body, and often a membranous structure. Upon insemination, breakdown of the cortical alveoli and elevation of the chorion began around the animal pole and ended at the vegetal pole. It was found that the spherical body was extruded with the colloidal material from the CA: the spherical body swelled after the opening of an aperture and was extruded into the perivitelline space through a large aperture. The empty CA shrank and disappeared completely as a result of the transformation of its envelope to numerous microvilli. The spherical body isolated or in the perivitelline space could be digested quickly by proteolytic enzymes. When spherical bodies in the perivitelline space of a fertilized egg were digested enzymatically, the vitellus came into direct contact with the chorion. The present study seems to show that swollen spherical bodies derived from CA play a role in maintaining a certain distance between the chorion and the vitellus after fertilization.

Notes: Summary Mutants in the bithorax system ofDrosophila produce homeotic transformations that affect the mesothoracic, metathoracic and first abdominal segments. In the present report we describe a clonal analysis of the development of those mutants transforming the metathorax and first abdominal segments into mesothorax. The main results indicate that (1) The normal dorsal metathoracic (haltere) disk has similar developmental parameters to the dorsal mesothoracic disk. The main difference is that the initial and final numbers of cells are different in both disks. (2) In flies mutant forBithorax andpostbithorax (which transform the haltere into wing) the transformed haltere disk has the same initial and final number of cells as the normal wing disk. (3) In morphogenetic mosaics homozygousbithorax (andpostbithorax) clones express their genotype autonomously regardless of the genotype of surrounding haltere cells. This autonomy is expressed in a regulation of the number of adult cells per compartment, typical cell affinities and final cuticular differentiation.

Notes: Summary 1. The effect of ethidium bromide (EB) on ommatidium development inEphestia was investigated. Doses ranged from 10−3 to 10 μg EB/pupa. 2. Even the lowest dose applied blocked imaginal ecdysis. The degree of development toward the imago was progressively lower with increasing doses of EB. 3. The development of pigment in the retinula cells, which proceeds from the dorsocaudal portion of the eyeanlage in a ventrorostral direction, is usually completed in pupae which have received injections of up to 0.80 μg EB. Five μg prevents all further pigment development. 4. A peculiar deficiency phenomenon (Pigmentaussparung, PA) appears in animals treated with 0.90–3.00 ug EB. A band-shaped unpigmented region appears in an otherwise pigmented region. The area is perpendicular to the direction of successive development of ommatidia. The region appears to be undifferentiated histologically. 5. The location and width of the affected regions are dependent on dose and upon the age of the pupa when injected. They are coincident with the distribution of the 2 successive series of cell divisions which precede differentiation. 6. The results support the conclusion that the waves of cell division are a prerequisite for the appearance of all cell types in the ommatidium.

Notes: Summary The metabolic fate of amino acids introduced into the locust egg by the addition of amino acids after oviposition is compared to that of amino acids derived from the maternal haemocoel. It was found that amino acids from the two sources did not always follow the same pattern of utilization. Topical application resulted in some of the applied amino acids being converted into other amino acids and ammonia. When the labelled amino acid was administered to the egg via the maternal haemocoel, radioactivity was restricted to the amino acid orginally provided.

Notes: Summary The morphological features during development of diapause and non-diapause eggs of the silkworm,Bombyx mori, were investigated by means of light and electron microscopy, with special reference to eggs up to 24 h after oviposition. The blastoderm and yolk cells began to be formed about 6 and 24 h after oviposition, respectively, in both the diapause and non-diapause eggs, indicating that the diapause and non-diapause eggs develop at similar rates at least until 24 h after oviposition. Specific changes in the distribution of yolk granules were observed during early development of the diapause egg. Its yolk granules gradually aggregated into clusters from the periphery toward the inside of the egg during the period of blastoderm formation. Aggregation of yolk granules was most noticeable about 12 h after oviposition and then they dispersed again before yolk cell formation. On the other hand, yolk granules of the non-diapause eggs remained dispersed during development.

Notes: Summary The effects of the mutations eyeless dominant (ey D) and shibire (shi) on bristle pattern in the legs ofDrosophila melanogaster were examined. Both mutations cause gaps in the intersegmental membranes which separate leg segments and often alter the position of these membranes. It was observed that pattern disturbances including reversed bristle polarity and duplication of structures such as sex combs and transverse rows were associated with defects in the intersegmental membranes. The alterations in bristle polarity and most of the duplication of structures could be accounted for by a segmentally reiterated gradient in the legs which controls bristle polarity and which requires the integrity of the intersegmental membrane. A computer simulation of this gradient model was devised which accounted for the observed results. The possible role of cell death as a cause of the gaps in the intersegmental membrane and of some of the pattern disturbances was examined.

Notes: Summary The results of a combined morphological and biochemical study of the role of DNA synthesis during distal regeneration inHydra oligactis revealed that a burst of3H-thymidine incorporation into DNA preceded the elaboration of each of the initial three tentacles. In addition, the relative level of each burst of precursor incorporation relfected the number of tentacles formed at that time. Cytological localization of concentrated amounts of labeled material in nuclei of the hypostome and tentacle regions provided corroborative evidence for the biochemical findings. Evidence that the increased DNA specific activity levels described above are associated with tentacle initiation derived from studies in which regenerating hydra were cultured in hydroxyurea and studies in which hydra regenerated proximally rather than distally. Hydra regenerating in 8 mg/ml (0.105 M) hydroxyurea developed morphologically recognizable hypostomes but no tentacles, and incorporated3H-thymidine into DNA at a level distinctly below that exhibited by uncut, untreated animals. Similarly, hydra regenerated a normal, functional basal disc in the absence of any increased DNA specific activity. Therefore, it is suggested that tentacle initiation inH. oligactis requires concomitant DNA synthesis and, as such, represents an epimorphic phenomenon.

Notes: Summary In order to investigate the ultrastructure of the migrating cells in anuran gastrulae, three anurans, which belong to three different genera, were observed with transmission electron microscopy supported by light microscopy of the 1 μm sections and scanning electron microscopy. Fine filopodial cell processes, as well as cell processes probably flattened against the inner surface of the blastocoel wall, were formed by the migrating cells. Blebs and lobopodial cell processes were frequently observed inBufo, sometimes inXenopus, but not observed inRana. Microfilaments were observed in the cell processes. Focal close contacts, probably having adhesive properties, were made between the migrating cells and the inner surface of the blastocoel wall. These observations suggest that the cells migrate along the inner surface of the blastocoel wall by forming filopodia and pseudopodia flattened against the wall. The role of the blebs and lobopodial cell processes requires more investigation.

Notes: Summary The content of neuraminic acid (NA) of different developmental stages of trout eggs was determined. 1. The total NA increases from about 13 μg NA per egg (6–8 weeks before spawning) to 50 μg directly before spawning until hatching. 2. In freshly hatched fish larvae the NA-content is decreased to about 40 per cent as compared with stages before hatching. 3. The ratio of bound to free NA decreases from values of about 13.5 (6–8 weeks before spawning) to 0.85–1.2 at the hatching-stage. 4. The bound NA is almost entirely bound to sialo-glycoproteins.

Notes: Summary The distribution of tritiated (3H) uridine or its derivatives in embryos of the kelp flyCoelopa frigida is analyzed by autoradiography. The radioactive label is introduced into the growing oocyte, after injectio into females at different time periods post eclosion. The majority of the label remains in the cytoplasm for the entire embryonic development and is presumably incorporated into stable RNA. Only when the precursor is injected toward the final stages of oogenesis, can presence of label be detected in the nuclei, for a short time period during the blastodern stage. Since no preferential location in nucleoli is found, it appears possible that labeled cytidine could have been derived from the original precursor which would be available for incorporation into DNA.

Notes: Summary The early embryonic development ofPimpla is characterized by a complicated temporal and spatial pattern of ooplasmic movements detected in time-lapse films made during cleavage. The modified movements observed after the architecture of oviposited eggs had been altered artificially by centrifugation indicated that there are different dynamic systems for ooplasmic streaming, contractions, and nuclear migration. The discovery that unlaid, explanted oocytes ofPimpla can be activated by mechanical deformation provided a new way of studying alterations of egg architecture, nucleocytoplasmic interactions, and the control of morphogenetic processes during cleavage and blastoderm formation. In this article, development and ooplasmic movements in explanted oocytes with and without articifial activation are described and compared with those observed in eggs after normal oviposition. Four categories of explanted “eggs” can be distinguished: 1. Inexplanted eggs which are not activated by mechanical deformation, no movement of egg plasm can be observed, and nuclear multiplication never takes place. Thus the completion of meiosis as well as the ooplasmic movements must be triggered by deformation of the egg in the ovipositor. 2. Inartificially activated eggs with diphasic blastoderm formation, the following deviations from normal development are registered. The mixing motion at the anterior end of the egg, the transfer flow, and the forward component of the fountain flow are all absent. Instead, a homogenizing movement is observed in the ooplasm of the anterior region of the egg. The energids in this region then migrate directly to the periphery, and in due time form the blastoderm (first phase of blastoderm formation). In the posterior 2/3 of the egg, blastoderm formation is slightly retarded. The so-called mixing motion, the unipolar flow and the caudal part of the fountain flow take place as in normal development, and the energids become distributed throughout a central plasm column before they migrate radially to initiate a second phase of blastoderm formation. There are marked ooplasmic contractions at the egg poles. 3. Forartificially activated eggs with successive blastoderm formation we recorded the same deviations from normal development as in the cephalic region of eggs of category 2. Blastoderm formation also occurs in due time. In the caudal region of the egg, a “dilated” unipolar flow is found. The fountain flow is reduced and greatly delayed. Energids migrating from the anterior egg region into the posterior may be carried to the posterior egg pole in a central plasm by the fountain flow. A peripheral, ring-shaped contraction moving in a posterior direction indicates the zone where the preblastoderm gradually forms. A marked antero-posterior time gradient is evident in blastoderm formation. Development of these eggs is greatly retarded up to hatching of the larvae. 4. Ineggs without blastoderm formation after activating treatment, no energids could be found apart from the meiotic nuclei. Nevertheless, the ooplasmic movement pattern and the histological aspect of these eggs sometimes resembled those of eggs oviposited by the female. Also, formation of pseudo-pole cells could be observed. These observations demonstrate that pseudocleavage takes place in such eggs. The streaming system is apparently able to achieve the pattern of ooplasmic movements independently of nuclear multiplication. Our observations demonstrate the autonomy of the streaming systems and of energid migration. The third dynamic system, ooplasmic contractions, occurs in artificially activated eggs combined with the streaming system and/or nuclear multiplication. It may possibly act independently in the very early contractions at the egg poles; these may be comparable to events at the elevation of a fertilization membrane. The discussion concerns exogeneous and endogeneous factors which may affect the pattern of movements, and the functions of mixing motion and unipolar flows in restricting the early nuclear migration to the central plasm. Also discussed are the significance of the anterior and posterior initial regions (“Initialbereiche”) and ofsuccessive blastoderm formation with respect to the relation between long-germ and short-germ egg types.

Notes: Summary 1. Data on the natural occurrence of the microgyne form ofMyrmica rubra L. are given, showing it to be more common than previously suspected. 2. Morphometrics show that the microgynes are an isometric reduction of the normal queens. 3. Experimental evidence is given to show that microgynes tend to breed true and that they have a queen effect that is similar to normal queens. 4. The origin of the microgyne polymorphism is discussed and it is concluded that it is genetic, microgynes perhaps being an atavistic form of the species.

Notes: Résumé L'enregistrement de l'activité des ruches sur un appareil d'un type nouveau montre des fluctuations journalières très marquées. Elles ne sont pas en accord avec les variations thermiques ni avec les variations de l'activité solaire. Elles diffèrent beaucoup d'une ruche à l'autre, même quand les ruches sont placées côte à côte. L'enlèvement de tout le couvain, ou au contraire l'introduction de dix cadres de couvain, ne modifie pas visiblement ni rapidement l'activité. Il s'agit très probablement d'un accident statistique. Par contre, l'enregistrement sur huit jours qui efface ces accidents est en bon accord avec les variations thermiques.

Notes: Summary The number of ovarioles was examined in the ovaries of 11 species ofVespula Thomson, 4 species ofDolichovespula Rohwer and 8 species ofVespa L.Vespula andDolichovespula generally have 6 ovarioles per ovary; onlyVespula sulphurea (Saussure) andVespula squamosa (Drury) have 7+7 ovarioles. In the genusVespa the number of ovarioles varied from 7+7 to 10+12. In some species such asVespa orientalis Linnaeus the number was constant (7+7); in others it varied even between the two ovaries of the same specimen. No significant difference was found in the number of ovarioles between queens and workers. The ovarioles of mature egg laying queens in summer were much longer than those of workers. The number of ovarioles inVespa tropica trimeres Van der Vecht is 9+9, 10+10, 10+12, whereasV.t. pulchra Buysson has only 7+7. This finding together with the considerable differences in body color suggest that the two forms belong to different species.

Notes: Zusammenfassung 34 überwiegend komplette Völker der Gastameise wurden während der Ueberwinterung in zwei polycalenFormica polyctena Foerst.—Kolonien gesammelt. Die meisten der Völker bestehen aus einer Anzahl von Intermorphen (Tieren, die morphologisch zwischen Arbeiterin und geflügeltem Vollweibchen stehen) und einer größeren Zahl echter Arbeiterinnen (Ergatomorphen). Nur in 12 von den 34 Völkern fanden wir entflügelte Weibehen (Gynomorphe). Durch Präparation aller Gynomorphen, Intermorphen und einer repräsentativen Anzahl von Ergatomorphen konnten wir zeigen, daß jedes Volk nur ein fertiles Weibchen besitzt, das sich durch ein mit Sperma gefülltes receptaculum seminis und lange Ovariolen mit corpora lutea an der Basis auszeichnet. In 22 der 28 Völker mit einer Königin war dies eine Intermorphe. Wir fanden nur 6 gynomorphe Königinnen. Echte Arbeiterinnen (ohne Ocellen) waren bis auf eine Ausnahme niemals begattet oder fertil. Neben der Königin konnten wir in 14 von 19 größeren Völkern (ohne Koloniegründungen) (=75%) eine oder mehrere (bis 40 in einem Volk) Intermorphe und Gynomorphe mit gefüllten receptacula beobachten. Sie hatten jedoch stets kurze Ovariolen ohne corpora lutea. Wir nehmen an, daß diese überzähligen begatteten Weibchen durch einen bisher unbekannten Mechanismus steril gehalten werden, so wie beiLeptothorax gredleri Mayr. Die mögliche Bedeutung dieser «funktionellen Monogynie für die Gastameise wird diskutiert. Einige sehr kleine Völker mit nur einem fertilen Weibchen, ohne oder mit wenigen Arbeiterinnen und einigen Larven betrachten wir als Koloniegründungen. Neue Völker scheinen durch einzelne begattete Weibchen gegründet zu werden.

Notes: Résumé Ce travail est consacré à l'étude des individus neutres mermithisés présents dans les sociétés de la fourmiPheidole pallidula. L'infestation se produit pendant la fin du 3e stade larvaire de la fourmi, lorsque la larve prend une teinte orange et mesure entre 1,30 et 1,40 mm. Cette période correspond à la phase de différenciation pendant laquelle la larve s'oriente dans les nids sains vers la caste ouvrière ou vers la caste soldat. Dans les nids parasités et en fonction du moment exact de l'infestation la larve de fourmi donne une ouvrière parasitée, rarement un soldat parasité et fréquemment unintercaste parasité. Nous assimilons lesintercastes à desmedia disparus dans les colonies saines dePheidole pallidula et non à des soldats modifiés (mermithostratiotes deVandel). Nos arguments sont les suivants: - Il existe de véritables soldats parasités dont la tête, bien que réduite, garde toutes les caractéristiques de la caste. Ce sont ces soldats parasités qui méritent le nom de mermithostratiotes. - L'analyse biométrique de la tête des intercastes permet de les intercaler exactement entre les ouvrières et les soldats. - Le pourcentage des soldats sains dans les colonies parasitées est exactement le même que celui des soldats dans les colonies saines. Les intercastes ne sont donc pas prélevés sur le contingent des soldats. - Les intercastes présentent une féminisation plus ou moins importante marquée par la présence d'un ocelle plus ou moins développé. On a montré que le degré de développement de l'ocelle est directement lié au nombre de vers présents dans l'intercaste (jusqu'à 5) ainsi qu'à la date de l'infestation.

Notes: Résumé La stridulation deAcromyrmex octospinosus Reich. est étudiée d'une manière descriptive en deux étapes: La première définit les paramètres et coefficients de forme de l'organe stridulateur (pars stridens) selon les groupes morphologiques. Une comparaison des données absolues et regressées est faite avecAtta cephalotes d'après les résultats deMarkl (1968). La seconde étape est représentée par l'analyse acoustique du bruit émis. Les cadences, les niveaux sonores, la spectrographie des fréquences et l'oscillographie des émissions sont étudiés selon les groupes.

Notes: Résumé Un nid deParavespula germanica a été élevé, en conditions semi-naturelles, pendant la deuxième partie de sa vie. Au cours de cette période, nous avons enregistré l'activité de vol (mesurée par le nombre d'ouvrières rentrant au nid) en même temps qu'étaient effectués des prélèvements d'ouvrières afin de déterminer la nature des charges rapportées au nid. Ces résultats ont été confrontés avec les enregistrements des données climatiques: température et hygrométrie. La ≪rentabilité≫ de l'approvisionnement n'est pas constante, c'est-à-dire qu'un pourcentage variable d'ouvrières rapporte effectivement des charges au nid. L'analyse statistique montre qu'il existe une corrélation positive entre l'activité de vol et la rentabilité de l'approvisionnement. Cette analyse a permis de préciser l'influence relative des facteurs climatiques sur cet approvisionnment. Si l'hygrométrie ne semble pas intervenir (dans les limites de notre observation), la température se révèle avoir une action sur l'approvisionnement, non pas en modifiant l'activité de vol, mais en modifiant la proportion des ouvrières rapportant quelque chose. L'existence de ces corrélations implique que les variations de température entraînent d'importantes modifications dans l'économie du guêpier.

Notes: Résumé Attaphila fungicola est une petite Blatte aptère qui habite les nids d'Atta texana et d'Atta cephalotes. Les systèmes glandulaires et sensoriels sont réduits. Les palpes maxillaires présentent une structure complexe qui n'a jamais été décrite. Le grand développement de l'arolium permet aux femelles de cette espèce de s'accrocher fortement aux reines d'Atta pendant l'essaimage. Ce mécanisme permet une large diffusion de l'espèce.

Notes: Zusammenfassung Formicoxenus nitidulus lebt als Gastameise in den Nesthügeln vonFormica-Arten, wo sie ihre eigenen kleinen Nestchen bewohnt, jedoch von ihren Wirten Futter bekommt. Wir entwickelten eine Methode, diese Ameise in Abwesenheit der normalen Wirte zu züchten. Arbeiterinpuppen des nahe verwandten selbständigenLeptothorax acervorum werden zu Völkern der Gastameise gesetzt. Sie schlüpfen darin und arbeiten wie die Sklaven in Nestern dulotischer Ameisenarten. Wir konnten solche künstlich gemischten Völker bisher über mehr als ein Jahr halten. In einem künstlichen Temperaturcyclus erhielten wir daraus in diesem Jahr zwei Geschlechtstierbruten. Einige beobachtungen über die Ernährung der Larven, die Larvalentwicklung, die Produktion von Arbeiterinnen, Intermorphen und geflügelten Weibchen sowie Männchen werden beschrieben. Intermorphe Weibchen können ebenso wie geflügelte als Königinnen fungieren. Ihre weibliche Nachkommenschaft enthält jeweils alle verschiedenen Morphen.

Notes: Summary The ability of hornet workers (Vespa orientalis, Vespinae, Hymenoptera) to build geotropical oriented stems and combs has been tested in containers of various geometrical shapes. It was found that hornets display negative geotropism, but the capacity to discriminate the zenith, i.e., the highest point in the container, is not fully developed at eclosion but improves with times during the first 3 days of life.

Notes: Summary The natural honey bee nest was studied in detail to better understand the honey bee's natural living conditions. To describe the nest site we made external observations on 39 nests in hollow trees. We collected and dissected 21 of these tree nests to describe the nest architecture. No one tree genus strongly predominates among bee trees. Nest cavities are vertically elongate and approximately cylindrical. Most are 30 to 60 liters in volume and at the base of trees. Nest entrances tend to be small, 10 to 40 cm2, and at the nest bottom. Rough bark outside the entrance is often smoothed by the bees. Inside the nest, a thin layer of hardened plant resins (propolis) coats the cavity walls. Combs are fastened to the walls along their tops and sides, but bees leave small passageways along the comb edges. The basic nest organization is honey storage above, brood nest below, and pollen storage in between. Associated with this arrangement are differences in comb structure. Compared to combs used for honey storage, combs of the brood nest are generally darker and more uniform in width and in cell form. Drone comb is located on the brood nest's periphery. Comparisons amongApis nests indicate the advanced characters inApis mellifera nests arose in response toApis mellifera's adoption of tree cavities for nest sites.

Notes: Summary The density of a subducting plate is shown to become greater than the density of the adjacent mantle rock at a subduction depth on the order of 60 km. The density increase results from high pressures generated within the plate during its motion into mantle rock whose long-term strength is much less than the long-term strength of the plate. This positive density contrast between the plate and mantle is in addition to any positive density contrast that may result from the plate not being in thermal equilibrium with the adjacent mantle rock. The effect of this pressure induced density contrast on the overall down-dip stress distribution in the plate is shown to be insignificant on earthquake formation except, possibly, near the upper, near-surface portions of the plate. Implications of this result in terms of the inclusion collapse theory of deep earthquakes are discussed.

Notes: Summary Energetic electrons are continually removed from the radiation belts by resonant pitch-angle scattering with ELF turbulence. A realistic simulation of the concomitant precipitation loss of such electrons to the atmosphere shows it to be a significant source for the nocturnal ionospheric D-region. During geomagnetically quiet (non-storm) periods, precipitating electrons are expected to provide the dominant nocturnal ionization source at medium invariant latitudes corresponding to field lines just inside the plasmapause. When the level of scattering turbulence is high the quiet time precipitation can dominate for an extended range of latitudes (Λ∼ 55° to 65°). Observed fluctuations in the level of scattering turbulence should produce modulations in the concentration of nocturnal middle latitude D-region electrons which may be detected using radio probing techniques.

Notes: Summary The electrostatic force between a charged conducting sphere and a charged dielectric sphere in a uniform, arbitrarily oriented external electric field is obtained and presented in terms of force coefficients which depend only on the relative geometry of the two spheres and the dielectric constants of the dielectric sphere and the medium. When the dielectric constant of the dielectric sphere is allowed to approach infinity, the resulting computed force agrees with that ofDavis (1964) for two conducting spheres, and when the external field and the charge on the dielectric sphere are set to zero, the resulting force agrees with that ofHall andBeard (1975) for a charged conducting sphere near an uncharged dielectric sphere.

Notes: Summary A mathematical structure that takes into account the spatial non-uniformity of the source field distribution has been applied to geomagnetic data collected in Nigeria. A heuristic modelling technique, whose inverse exists, has been employed to obtain four-to sixlayered conductivity models of the earth. The results represent further delineation of fine structure in the sub-surface profile beneath Nigeria. An attempt is made to correlate these results with the feasible geological structure of the area.

Notes: Résumé On fait une application particulière de la théorie de la corrélation et de la régression pour l'interprétation des données résultant d'une prospection magnétique. Est déterminée, en premier lieu, la corrélation multiple entre l'intensité de la composante verticale du champ magnétique, la teneur en Fe et la profondeur d'un complexe porteur de minéralisations de fer. Le seconde partie de l'ouvrage présente un modèle d'estimation du contenu de fer et du volume de complexe minéralisé sur la base des courbes de régression déterminées. Dans la troisième partie du travail est effectué un calcul des erreurs d'appréciation de la qualité et de la quantité des réserves.

Notes: Summary In investigating the dynamic processes of the generation of stress waves in the nearest zone of seismic sources, questions concerned with their frequency pattern are very important. In this paper the frequency content of stress waves is expressed by the relative width of their amplitude spectrum. Measurements of stress waves close to a spherical explosive source in gravel-sandy soil, in loess, and in limestone have been realized earlier. This paper discusses the dependence of the frequency content of stress waves on the physical parameters of the medium, on the size of the charge and on the distance from the source.

Notes: Summary The atmospheric electric potential gradient was recorded continuously by a field mill at Fargo, North Dakota, for the period August, 1972–March, 1973. Hourly averages were taken by the equal areas technique to eliminate short period variations. The diurnal variation of monthly averages is shown for the fair weather periods and all weather. In addition, the diurnal variation is shown for all positive values of the potential gradient, which excludes periods of major local space charge generators, but includes periods when the potential gradient might be influenced by regional conditions not otherwise present during fair weather. For a given month the diurnal variation curves are generally similar, with the fair weather curve giving the highest values, and all weather curve giving the lowest values. The months September–November have similar curves with the lowest values and least deviation from the average. The months December–February have similar curves with the highest values. Harmonic analysis is used to compute the times of maxima and contributions to variance of the first four harmonics for each diurnal variation curve. The fair weather first harmonic accounts for the majority of variance and has a maximum near 19.5 h GMT. It is attributed to the global diurnal variation of potential gradient due to thunderstorm activity in the tropics. The second harmonic has one maximum occurring from 9–12 h local time and is attributed to the ‘austausch’ effect of convection, where ions affect the conductivity of the air locally. The differences in these monthly diurnal variation curves emphasize that the season of year, weather conditions, and length of time over which data is averaged must be specified in atmospheric electricity studies if meaningful conclusions are to be drawn.