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Georg Pencz als Maler
(1966)
1. The migration of the spotted mackerel, Pneumatophorus tapeinacephalus distributing in the coastal sea of Japan was investigated in relation to the geographical distribution of the fishing grounds, seasonal change of fishing condition. sea conditions and fork length. Secondarily, some anatomical and histological observations were carried out on spotted mackerels caught in the coastal sea area around Kagoshima and its vicinity to clarify the sex differentiation and the seasonal cycle of the gonads. 2. Spotted mackerels are distributed throughout a wide sea area stretching from north of Formosa to the south of Japan Sea. including the Pacific coastal sea from Kyushu to Chiba Prefecture. The northern limit of the distribution area is assumed to be the sea areas off San-in and Chosi. 3. The schools of adult fish make a feeding migration to the circumference of Saishu Island and to the sea area off Ashizuri cape in summer. and these schools make a spawning migration toward the sea area around the Osumi Islands and the southern area of the East China Sea in winter. 4. In winter some schools of adult fish remain living in the sea area south of the Izu Islands. These schools belong to a group isolated incompletely from that of the East China Sea. as some of them are those which came from the East China Sea. 5. The larvae grow while they are being brought by the sea current or tide current. When they have reached 50~60mm. in total length. they aggregate in schools and approach the coast. In spring they swim in the coastal nursery grounds. 6. From summer to autumn, the schools of the young fish make a feeding migration to the sea off San-in and to the eastern coastal sea of Chiba Prefecture. In winter. they make a seasonal migration to the coastal sea of South Kyushu, the East China Sea and the southern sea area of the Izu Islands. 7. The range of vertical distribution of the larvae is supposed to be the layer from the surface to 40m. in depth. The vertical distribution of the adult fish is chiefly in the layer, 40-70m. in depth, during the period from late autumn to early spring. It becomes shallower in late spring and summer, the depth being about 20-40m. 8. The ranges of water temperature and salinity in the sea where the adult fish schools are distributed are 17.0-26.0°C and 34.0~34.8%0. respectively. 9. The spawning takes place during the period from the end of January to June in the southern part of the East China Sea and the sea areas around the Osumi Islands, off Ashizuri Cape and around the Izu Islands. These spawning grounds are sea areas where a comparatively rapid current is running towards a land shelf. 10. The ranges of the optimum water temperatures and salinities for the spawning are assumed to be 17-23°C and 34.0-34.8 0/00, respectively. 11. The primordial germ cells seem to migrate to the gonad by amoeboid movement from other places than the gonad. 12. The early indifferent gonad is very slender and suspended with a mesogonium, in the coelom. It is composed of peritoneal epithelium, stroma cells and primordial germ cells. 13. The formation of the gonocoel begins as a longitudinal depression on the surface of the gonad, facing the mesentery. This depression takes place in the gonad of the fish, about 60mm. in fork length, prior to the sex differentiation. 14. The sex differentiation occurs directly without a phase of a juvenile hermaphrodite. 15. The gonad in which the gonocoel is greatly enlarged becomes an ovary, while that in which the gonocoel is left narrow becomes a testis. 16. In the early ovary the layer containing oogonia is surrounded with stroma cells. The surface of the ovary is covered with cuboidal epithelium. 17. In the ovary of the fish, 100-130mm. in fork length, the wall of the ovocoel forms small protuberances, which become the lobes of the ovary. The oocytes are situated in these lobes. The yolk formation begins in the oocytes, 15.....,20.a in diameter, 18. The maturing process of eggs is clasified into the following 7 stages; the chromatin nucleolus, the peripheral nucleolus, the yolk vesicle, the early yolk globule, the late yolk globule, the migrating nucleus and the matured stage. Ovarian eggs at the migrating nucleus stage and the matured stage are observed in the fish, more than 300mm. in fork length. 19. The surface of the early testis is covered with peritoneal epithelium. The interior is filled up with the multiplied stroma cells and the spermatogonia scattered among them. In the testis of a somewhat later stage, a lot of branches are stretched out of the testocoel. Some of the spermatogonia are arranged directly beneath the peritoneal epithelium and the others are buried deep in the testis. The testis lacks a layer of stroma cells under the peritoneal epithelium. 20. In the testis of young male fish the spermatogonia increase in number and surround the small branches of testocoel; they form seminiferous tubules. The testocoel and its large branches become the rete apparatus constructed of collecting ducts. The maturation division appears in the testes of the fish more than 280mm. in fork length. 21. The sex ratio of the young fish is approximately 1 : 1. The ratio between the gonad length and the fork length shows an exponential increase. The gonads of adult fish are enlarged about 9-13 % of the original length during the spawning season. 22. During the months from July to November the oocytes in the ovaries of adult female :fish are at the chromatin nucleolus stage and the peripheral nucleolus stage. During the same season there are only spermatogonia in the testes of adult male fish. The gonads of adult fish begin to increase in size in December and become the largest in March and April. The increase in size of the ovary is chiefly due to the enlargement of ova on account of yolk deposition. The increase in size of the testis is due to accumulation of spermatozoa. 23. A few oogonia can be seen m the ovanes of adult female fish during and immediately after spawning. Numerous spermatogonia appear along the inner walls of the seminiferous tubules late in the spawning season.
1. Bretolet, Wallis, wurde versucht, für verschiedene Oscines-Arten die Jahres- und tageszeitliche Häufigkeitsverteilung der Durchzügler innerhalb gegebener Zeitabschnitte zu ermitteln. Dass sich die beiden Pässe verglichen mit Beobachtungsstationen im Flachland oder an den Küsten dazu in besonderer Weise eignen, wurde bereits von anderen Autoren gezeigt; wesentlich ist, dass ortsspezifische, vor allem die tageszeitliche Häufigkeitsverteilung beeinflussende Besonderheiten bei der Beurteilung der so gewonnenen Zugmuster nicht ausser acht gelassen werden, weshalb sie gleich einleitend (S. 171-173) ausführlich besprochen werden. Einige Zugmuster-Eigentümlichkeiten liessen sich im Verlaufe der Analyse als Ausdruck spezifischer Biotoppräferenzen deuten (Seiten 2?8-209). Ein Vergleich der Zugmuster verschiedener Arten ergab auffällige Unterschiede zwischen Lang- und Kurzstreckenziehern und gestattete eine neue Deutung der biologischen Bedeutung von Nachtzugverhalten. 2. Um wenigstens bei einer Familie einen möglichst repräsentativen Querschnitt durch die Zugmuster von ausgeprägten Zugvögeln und weniger zuggeneigten Arten zu erhalten, wurden die auf Cou und Bretolet durchziehenden Ammern besonders eingehend untersucht und zum Zugverhalten weiterer Ammernarten kurze Hinweise gegeben. Bei weiteren Oscines-Familien wurden nach Möglichkeit Arten mit verschiedenem Zugverhalten aus derselben Gattungsgruppe ausgewählt, um dieverschiedenen Differenzierungen im Zugmuster deutlich werden zu lassen. 3. Beim Vergleich der Zugmuster von ausgeprägten Zugvögeln (Transsaharazieher) und weniger zuggeneigten Arten (Winterquartier erstreckt sich südwärts höchstens bis in den Mittelmeerraum) lassen sich folgende allgemeine Tendenzen erkennen: a) Die im Herbst an einem bestimmten Beobachtungsort ermittelte Individuenzahl von Durchzüglern ist bei ausgeprägten Zugvögeln von Jahr zu Jahr konstanter als bei weniger zuggeneigten Arten. b) Zugbeginn, Zughöhepunkt und Zugende einer Zugsaison streuen in aufeinanderfolgenden Jahren weit weniger bei ausgeprägten Zugvögeln als bei weniger ausgeprägten. c) Eine ± kontinuierliche jahreszeitliche Häufigkeitsverteilung der Durchzüigler ist bezeichnend für ausgeprägte Zugvogelanen, ein sprunghaftes Zugmuster dagegen für weniger zuggeneigte Arten. d) Die Durchzugsdichte, d. h. das Verhältnis der Durchzüglerzahl zur Zeitspanne der Hauptdurchzugsperiode, ist bei ausgeprägten Zugvögeln höher als bei weniger ausgeprägten. e) Je ausgeprägter das Zugverhaltell einer Art, umso eindeutiger ist die Tendenz zur Gipfelbildung in der tageszeitlichen Häufigkeitsverteilung der Durchzügler und umso konstanter sind Lage und Streuung dieses tageszeitlichen Zuggipfels. Ferner zeigen sich hinsichtlich Lage und Dauer der zum Ziehen verwendeten Tageszeit folgende Tendenzen: f)Früh wegziehende Langstreckenzieher wandern vorwiegend nachts (Ausnahmen: Schwalben und etwas weniger ausgeprägt einige Motacilliden). Innerhalb nah verwandter Artengruppen ist die Neigung zu Nachtzug umso grösser, je weiter die Art zieht. g) Arten, die weniger weit ziehen und .deren Winterquartier kaum weiter südwärts reicht als bis ins Mittelmeergebiet, sind meist typische Tagzieher (Ausnahmen: Sommergoldhahnehen Regulus Ignicapillus und Rotkehlchen Erithacus rubecula). h). Wenir zuggeneigte Arten ziehen täglich meist nicht mehr als 6 Stunden und zwar vorwiegend in den Morgendämmerungsstunden. i) Einige vergleichsweise spät im Oktober ihren Zughöhepunkt erreichende und bis in den Mittelmeerraum ziehende Arten können in ausgeprägter Form sowohl als Tag- als auch als Nachtzieher auftreten . 4. Da die Insetenmasse in den gemässig ten Breiten mit Beginn der kalten Jahreshälfte einem weiträumigen und sprunghaften Rückgang unterliegt, müssen Vogelarten, die auf Insektennahrung spezialisiert sind, beondere Zugverhaltensweisen entwickeln. Ein frühzeitig, d. h in einer Jahreszeit, in der die Nahrung noch im überfluss vorhanden ist, einsetzender weitreichender Wegzug muss den Vogel rechtzeitig aus dem Bereich der sprunghaften Nahrungsverknappung hinausbringen. Das zeitgerechte Eintreten der physiologischen Zugbereitschaft wird durch eine entsprechende Kopplung des biologischen Rhythmus des Vogels mit einem geeigneten Zeitgeber aus der Umwelt bewirkt; unmittelbar zugauslösend werden wohl endogene Faktoren wirken. Die für Langstreckenzieher bezeichnenden Zugmustereigenschaften (siehe 3a-e) werden als Ausdruck einer solchen Zeitgeberkopplung und endogen wirksamen Zugauslösung gedeutet. 5. Auf pflanzliche Nahrung spezialisierte oder entsprechend anpassungsfähige Vogelarten zeigen ganz andere Zugmustereigenschaften (siehe 3a-e). Die allmählichere Veränderung des pflanzlichen Nahrungsangebotes und die gewöhnlich nur regional beschränkte Unzugänglichkeit der Nahrung erlauben es, den Wegzug auf ein Minimum zu beschränken. In zunehmendem Masse scheinen nun unmittelbar lebensnotwendige Umweltfaktoren wie Nahrung, Witterung u. ä. das Zuggeschehen zu beeinflussen (Seiten 206-208). Auf die Zugmustereigenschaften, die dies zum Ausdruck bringen, wird ausführlich eingegangen. 6. Bei der weiteren Analyse der Zugmuster wird vor allem der biologische Sinn des Nachtzuges zu deuten versucht. Die unmittelbaren Kausalfaktoren oder endogenen Mechanismen, die das Äussern von Nachtaktivität ermöglichen, werden dagegen nur am Rande gestreift. An Beispielen wird aber gezeigt, dass Nachtaktivität auch während der Brutzeit zumindest potentiell zu einem allgemeineren Reaktionsvermögen vieler Vogelarten gehört (Seiten 210-211) und dass die nächtliche Zugaktivität nicht als Ausdruck einer generellen Umstellung von ausschliesslicher Tagaktivität während der Brutzeit auf partielle Nachtaktivität zur Zugzeit verstanden werden darf. Unter den auf Cou und Bretolet durchziehenden Oscines konnte Nachtzug vor allem bei früh aufbrechenden Weitstreckenziehern und bei ausgeprägten Flatterfliegern festgestellt werden. Es werden auch Beispiele für ähnlich Korrelationsverhältnisse bei Nonpasseres angeführt (Seite 213). Tagzug zeigt sich dagegen im typischen Fall bei relativ spät wegziehenden Kurz- und Mittelstreckenziehern (nicht Transsaharazug) und unter den Nonpasseres bei Arten, die zu Gleit- und Segelflug neigen. Für die früh aufbrechenden Weitstreckenzieher und die Flatterflieger muss Nachtzug in thermoregulatorischer und wasserökonomischer Hinsicht gegenüber Tagzug wesentliche Vorteile bringen. Ferner resultieren bei grossen Entfernungen zwischen Brutgebiet und Winterquartier aus dem nächtlichen Zugmodus wesentliche Zeitgewinne, die sich beim Heimzug als besonders vorteilhaft erweisen. Abweichungen vom obigen Schema (z. B. Nachtzug bei Mittelstreckenziehern und Tagzug bei Langstreckenziehern) werden ebenfalls diskutiert und zu erklären versucht (Seite 215). In Anpassung an bestimmte ökologische Gegebenheiten ist Nachtzug damit gegenüber Tagzug eine Reaktionsweise mit hohem positivem Selektionswert.
An attempt has been made in this article to critically survey the field of low Reynolds number flows, with particular regard to the hydrodynamic resistance of particles in this regime. A remarkable burgeoning of interest in such problems has occurred wlthin the past decade. Significant advances have been recorded on both the theoretical and experimental sides, with the former gains far outdlstancing the latter m scope. Problems which would have been impossible to solve rigorously before the advent of singular perturbation techniques are now being regularly solved, though hardly in a routine fashion; insight, intuition, inspiration, and ingenuity are still the order of the day. For those interested in direct engineering applications of the material covered by this review, the perspective from which many of the more general results set forth here should be viewed is, perhaps, best illustrated by an example: The resistance of any solid particle to translational and rotational motions in Stokes flow may be completely calculated from knowledge of a set of 21 scalar coefficients (Section II,C,l). While it seems highly improbable to expect that all these coefficients could be experimentally measured in practice, except perhaps in the trivial case of highly symmetrical bodies for which many of the coefficients vanish identically, this does not detract from the conceptual advantages of knowing exactly how much one does not know. Having an ideal goal against which the extent of present knowledge can be gaged permits a rational decision as to how to optimize one's investment of time, effort, and money in the pursuit of additional data. Furthermore, with the development of high-speed digital computers it may soon be possible to calculate all these coefficients for any given body (O 1 b). The general theory provides a rigorous framework into which such knowledge may be embedded. Use of symbolic" drag coefficients" (Section II,C,2) and symbolic heat- and mass-transfer" coefficients" (Section IV,A) furnishes a unique method for describing the intrinsic, interphase transport properties of particles for a wide variety of boundary conditions. Here, the particle resistance is characterized by a partial differential operator that represents its intrinsic resistance to vector or scalar transfer, independently of the physical properties of the fluid, the state of motion of the particle, or of the unperturbed velocity or temperature fields at infinity. Though restricted as yet in applicability, the general ideas underlying the existence of these operators appear capable of extension in a variety of ways. A recurrent theme arising throughout the analysis pertains to the screwlike properties of particles and of their intrinsic right- and left-handedness (Sections II,C, 1; II,C,2; III,C and IV,B). Such properties reflect an inseparable coupling between the translational and rotational motions of the particle. Helicoidally isotropic particles furnish the simplest examples of bodies manifesting screw-like behavior. These particles are isotropic, in that their properties are the same in all directions. Yet they possess a sense, and spin as they settle in a fluid. These id eas are likely to be of interest to microbiologists, biophysicists, geneticists, and others in the life sciences for whom handedness and life are intimately intertwined. The microscopic dimensions of the objects of interest to them insures ipso Jacto that the motion takes place at very small Reynolds numbers. Readers interested in an elementary but broad survey of sense in the physical and biological sciences are referred to Gardner's delightful book "The Ambidextrous Universe" (01). First-order corrections to the Stokes force on a particle, arising from wallor inertial-effects, can be directly expressed in terms of the Stokes force on the body in the absence of such effects. Thus, with regard to wall-effects in the Stokes regime, Eq. (135) expresses the force experienced by a particle falling in, say, a circular cylinder, in terms of the comparable force experienced by the particle when falling with the same velocity and orientation in the unbounded fluid. Equation (139) expresses a similar relationship for the torque on a rotating particle in a circular cylinder, as does Eq. (166) for the first-order interaction between two particles in an unbounded fluid in terms of the properties of the individual particles. Analogously, Eq. (234) expresses the inertial correction to the Stokes drag force in terms of the Stokes force itself. A comparable relationship exists (Section IV, A) between the heat-transfer coefficient at small, nonzero Peelet numbers and the heat-transfer coefficient at zero Peelet number-that is, the coefficient for conduction heat transfer. Finally, Eqs. (78)-(79) (or their symbolic operator counterparts) permit direct calculation of the Stokes force and torque experienced by a particle in an arbitrary field of flow solely from knowledge of the elementary solutions of Stokes equations for translation and rotation of the particle in a fluid at rest at infinity. The utility of already available knowledge is thus greatly extended by the existence of such relations. It permits one whose interests lie entirely in the macroscopic manifestation of the motion, e.g., the force and torque on the body, to bypass the oftentimes difficult problem of obtaining a detailed solution of the equations of motion, and to proceed directly to the computation of the force and torque on the body from the prescribed boundary conditions alone. The calculation is thereby reduced to a quadrature. The contents of this review may be read simultaneously from two different points of view. First and foremost it may be regarded as a compendium of recent advances in low Reynolds number flows. Secondly, from a pedagogic viewpoint it may be profitably used to illustrate the direct application of invariant techniques, that is, vector-polyadic and tensor methods, to a class of physical problems. Because of the relative simplicity and rich variety of physical problems associated with low Reynolds number motions, intuitive arguments may be employed to gain insight into the nature of polyadics and tensors; the role played by the concept of direction as a primitive entity is brought out here to a degree not usually found in standard works on tensor analysis.
Epilabidocera amphitrites is one of the most common copepods in the deep waters adjacent to Friday Harbor and shows characteristic swarming behavior in the surface film of the water from later spring through early summer. That the swarms are composed mainly, up to 99 %, of adult males appears to be due to difference in phototaxis to a weak light. This species, at least in copepodid stages, is omnivorous, but seems to prefer an animal diet rather than diatoms. Reproduction takes place continuously from early spring through autumn. The external anatomy of both the female and male has been described in detail. The cuticle forming the arthrodial membrane and the lining of the esophagus, hindgut, and hypostomal and labral troughs appears to be of the same nature throughout, consisting of a single stratum. The cuticle on the general body surface, however, consists of two main strata. The endoskeletal structures consist of two categories, the endoskeleton proper and the endoskeletal tendons. The former involves apodemes and apophyses. Of these the major ones are described in detail. The latter consist of two median tendinous endosternites in the « head », four pairs of ventral intersegmental thoracic tendons, and a pair of dorsal longitudinal tendons in the metasome. The endosternites are well developed, serving as origins for dilators to the atrium oris and esophagus and also for a number of extrinsic muscles to the head appendages. The skeletomusculature may be divided into longitudinal trunk and limb muscles. The paired dorsal and ventral longitudinal trunk muscles in the metasome extend, respectively, from the levels of the cervical groove and the post-maxillulary apodeme to the end of the metasome. The longitudinal trunk muscles in the urosome origate at the anterior end and run most of its length. They are arranged as paired dorsal and ventral groups and a pair of lateral muscles. The extrinsic limb muscles are described in detail. They originate either from the lateral to dorsal exoskeleton or from the endosternites. The digestive tract starts with the atrium oris in the oral cone, followed by the mouth proper, esophagus, midgut, and finally by the hindgut which opens as the anus at the end of the urosome. The oral cone consisting of the three lobed labrum and the paired paragnaths has a longitudinal groove, the oral groove, which is covered ventrally by the spinulose setae of the maxillae and laterally by the gnathobasal endites of the maxillules, these together forming an effective feeding apparatus. The midgut is produced anteriorly into a diverticulum which is higly secretory. In the middle portion of the midgut the epithelial cells are highly vacuolated. As they pass through this vacuolated region the gut contents are cemented into fecal pellets by a mucous secretion and they acquire a peritrophic membrane. There is a strong valve between the midgut and the hindgut. Peristalsis in the midgut is irregular but powerful and primarily in the reverse direction. The circulatory system involves a single heart, enclosed in a large pericardial space, and an anteriorly directed aorta terminating in an anterodorsal aortic sines. The latter communicates through three paires of openings with the sinuses in the head, which are in turn continuous with the perivisceral cavity, from which blood is returned to the pericardium. The heart has the form of a flask with an aortic valve at the tapered anterior end and a posterior ostium. The aortic wall is continued posteriorly over the heart and wraps around the anterior three-fifths as an outer membrane. This outer membrane is extended dorsally at three places to attach the heart to the dorsal exoskeleton; and it is also drawn out ventrally to form the anterior and lateral walls of the pericardium. These walls are continuous with the pericardial floor which seals the pericardia! cavity from the perivisceral cavity. The heart-beat and the blood flow through the system have been discussed. The excretory system consists of a pair of maxillary glands, each comprising a coelomic end-sac, a coelomic secretory tubule and an ectodermal excretory duct. The end-sac communicates with the tubule through a valvular opening. Antennary glands are not gound either in the nauplius stage or in the adult. The male reproductive system consists of a single testis and a single genital duct which is divided into four differentiated sections, the vas deferens, the seminal vesicle, the spermatophore sac, and the ductus ejaculatorius. The vas deferens is a thick-walled glandular tube secreting the various constituents of the spermatophore. The seminal vesicle serves mainly as a reservoir for the various components of a definitive spermatophore, and it is here that these take up their final positions. The spermatophore sac is highly glandular and is mainly responsible for formation of the coupling apparatus of the spermatophore. The spermatophore is not open directly to the outside but is connected with a canal system in the coupling apparatus. When transferred to the female genital segment at copulation, the central secretion of the spermatophore is discharged through the canal system of the coupling apparatus to glue down the spermatophore. A duct through which the spermatozoa can pass from the spermatophore to the spermathecae of the female appears to be formed later by an action of the female, possibly secretion of an enzyme or lysin. The discharge of the contents of the spermatophore is effected by swelling of Q-spermatozoa in the distal region of the spermatophore. The functional spermatozoa are spherical or polygonal and nonmotile. The female reproductive system consists of a single ovary, two oviducts, each with several diverticula, leading to the paired opnenings into the vaginal vacity, a pair of spermathecae and a pair of glands which open into the oviducts. In the mature female the oviducts are wide and sac-like, expanded by growing oocytes. However, the last portion of the oviduct is usually empty of eggs and is highly secretory. The oldest oocytes in the oviducts are usually at the metaphase of the first maturation division. The evidence points to the conclusion that the eggs are laid in this stage, and they are fertilized when they pass through the vaginal cavity. Oogenesis has been studied in detail. There are two periods of yolk formation: the first immediately after the dispersion of the mitochondrial bodies and the second in the last phase of the oocyte growth when the vacuoles in the cytoplasm are gradually replaced by yolk. Two dorsal ocelli, in the copepodid stages, are placed dorsolaterally against the exoskeleton and highly developed, each with a perfectly spherical, cuticular lens, while a single ventral ocellus remains unspecialized through the copepodid stages. Each dorsal ocellus proper is suspended in the head sinus by several connective tissue stands in addition to an aye muscle and consists of a large, syncytial pigmented cup occupied by a cellular sphere which is composed of 9 retinular and 4 crystalline cells. Each of the 9 retinular cells gives off an axon which leaves the ocellar cup at one of three places to proceed to the nauplius eye center in the protocerebrum. The ventral ocellus consists of two multinucleated pigmented cells, a cup-shaped tapetum, 6 retinular cells and about 8 conjunctival cells. Each of the 6 retinular cells sends an axon which loops over the posterior rim of the ocellar cup in common with the others to course to the nauplius eye center in the protocerebrum. The ventral ocellus is innervated by two afferent nerve fibers. There is also found a pair of conspicuous nerve fibers, possibly afferent, associated with the dorsal and ventral ocelli. A pair of accessory retinular groups, each consisting of three retinular cells, is found posterior to the dorsal ocelli. Three efferent aXOl1S from each group form a nerve running to the nauplius eye center in the protocerebrum. A pair of frontal organs, each innervated by a frontal nerve, lies in the anterior end of the head. The frontal nerves can be traced up to a pair of neuropiles immerdiately ventral to the nauplius eye center in the proto cerebrum. A pair of suprafrontal nerves branched off from the frontal nerves is found to innervate a pair of sensory filaments, the suprafrontal sensiIla, at the lower anterior end of the head. The central nervous system, consisting of a well developed brain connected by massive circumesophageaI connectives to the ventral nerve cord, has been described in detail. The ganglion cells are found throughout the nerve cord, and they are arranged into ganglia in the thoracic segments bearing the swimming legs. The stomatogastric nervous system has two pairs of labral and a single gastric ganglia. The medial pair of the labral ganglia forms anteriorly a single ganglion which is connected to the brain by three small nerves. The giant fiber system, consisting of giant motor fibers and giant interneurons, has been studied in detail, and it appears to constitute the effector portion of an escape reflex. The cutaneous glands opening through small pores in the cuticle of the metasome, urosome, and the appendages have been described. Chromatophores, unicellular or syncytial with several nuclei, are scattered deep in the body and are responsible for the metachrosis.
The surface tension sigma and the surface density thickness t of nuclear matter have been calculated in the Fermi-gas model, the nucleons moving in a self-made shell model potential with a realistic slope and velocity dependence ( parameters alpha and beta ). One gets the experimental values for sigma and t with alpha and beta agreeing with earlier data.
When filming in time-Iapse with low picture frequencies it is advantageous to work with an impuls method of operation, i. e. to switch in the camera for only a small proportion of the total time. The length of the exposure and the picture-frequency should be able to be regulated as independantly as possible from one another. The author discusses the possibilities given in this field and describes a suitable apparatus for the purpose.
The author examines different methods to avoid moisture condensation on observation windows caused by irregular temperature distribution. The respective measures consist of covering the window with a water-absorbent layer and heating with electrical current or through absorption of radiation. Furthermore, the culture-medium can be fixed in suitable cases on the observation window, through which photographs can be taken.