ALBERT

Description / Table of Contents: Summary 1.Rathkea octopunctata M. Sars is a north boreal circumpolar anthomedusan. A brief account is given on the general features of its distribution to the present date. In European waters the main area of distribution are the North Sea and adjacent waters. To the south the area of distribution extends into the Mediterranean and the Black Sea, and to the north into arctic boreal waters. 2. In the North Sea and most of the adjacent areas, the occurrence of the medusan is limited to the cold seasons of the year. It appears during the months of October to December, and is always to be found in small numbers in the winter plankton. In the spring, from April to May, there is a great increase in numbers, then within a brief time the medusa disappears almost entirely. In the Mediterranean and the Black Sea, the medusan was described as occurring during the spring, whereas it is a distinct summer form in the arctic boreal area. 3. The medusa has the remarkable ability to reproduce asexually by budding-off medusae. Two different generations of medusae are therefore to be recognized, i.e. a) the primary medusae originating in the ordinary way from medusa buds of the hydroid, b) the secondary medusae produced by the budding process on the manubrium of the primary medusac. The secondary medusae are also able to reproduce asexually in the same way and give rise to more generations so that the stock of medusae is increased. It is because of the asexual reproduction of the medusae that there is a rapid increase of stock during the spring. 4. Primary medusae and secondary medusae can be distinguished by morphometrical means as they exhibit a different ratio of height to width. 5. Comparison has been made of two different areas with regard to the seasonal occurrence of the medusan and the temperature conditions of its habitat. The two areas are the English Channel near Plymouth and the North Frisian Waddensee. In these areas the onset of seasonal occurrence and its duration are nearly the same. Comparative tests of their temperature conditions give the following results: a) the appearance of the medusan in the autumn starts during a period of rapidly falling temperature whereas the springtime abundance, the following period of sexual reproduction, and the more or less sudden disappearance, take place during a period of rapidly rising temperature; b) according to the time of first appearance of the medusan and its disappearance, the higher und lower limits of water temperature respectively are about 15 to 11° C and 11 to 15° C; c) the sexual reproduction takes place within rather narrow limits of temperature only. 6. For the North Frisian Waddensee the temporal and qualitative course of the change of reproduction from the asexual to the sexual has been demonstrated by the analysis of the reproductive behaviour of numerous medusae taken from plankton samples during the spring. Comparative tests of water temperature show that the critical temperature value for the change of reproduction is limited to about 7° C. 7. By rearing both the hydroid and the medusa generations in the laboratory under different temperature conditions, it has been proved experimentally that the essential phases of development and reproduction of Rathkea are dependent on the water temperature. 8. This has been proved first for the process of budding in the hydroid. The production of medusae buds in the hydroid preceding and causing the beginning of the appearance of the medusa in the autumn plankton takes place in the laboratory by lowering the temperature below a higher limit of about 14 to 12° C. 9. Secondly, the process of budding on the manubrium of the medusae is initiated by a falling temperature, and in general is confined to low temperatures below a critical limit of about 6 to 7° C. 10. The speed of budding, (i. e. of the process of formation and development of the medusa buds on the manubrium until their liberation), is slow in medusae kept in a falling temperature or in constant low temperature. Within the range of „budding temperature“ the speed of budding increases with rising temperature. If the temperature rises beyond the critical limit of 6 to 7° C, an increasing speed of budding will be observed at first, too. Then as a result of the rising temperature, the medusae cease the production of buds and start to develop gonads and to reproduce only sexually. 11. Rapid ripening of the gonads occurs at a temperature of about 8 to 9° C, and culmination of sexual reproduction takes place at temperatures of about 9 to 12° C. 12. Every medusan of both the primary and secondary generation is able to reproduce asexually first and then sexually, with the exception of the youngest generation of secondary medusae which was produced on the manubrium of medusae changing from asexual to sexual reproduction, and which reproduces only sexually. 13. Rising temperatures increase the mortality of medusae. It has been proved that a large portion of medusae experimentally exposed to temperatures of about 15 to 16° C will die without having succeeded in reproducing sexually. 14. The secondary medusae react in exactly the same way as the primary to a rising temperature, in particular, an increase in the speed of budding is the first reaction. Therefore, although the single medusan produces a greater number of offspring asexually in lower rather than higher temperatures, a greater increase in numbers results from rising temperatures owing to the quicker succession of generations, and finally the primary medusae and the older secondary ones represent only a small fraction of the entire stock. 15. The latent period, (i. e. the period during which no effect of the rising temperature is visible externally, and which is then followed by the resulting production of germ cells), will be shortened by rising temperature. Furthermore, this period is shorter in secondary medusae than in primary. This is to be explained by the fact that the secondary medusae are already affected by the rising temperature during the process of their formation. 16. The modifying influence of temperature on the medusae can be proved by the variation in growth when they are exposed to different temperatures. In low temperatures growth is slower but the final size is definitely larger than when growth has taken place in higher temperatures. 17. In the progressive succession of generations the youngest generation of secondary medusae is the smallest one owing to the shortening of the latent period by an increased temperature. Apparently, this is to be explained by the earlier start of sexual ripening. 18. The dependence of both methods of reproduction and of their change on temperature conditions has been proved by the following experiment, too. If ripe females, having first reproduced asexually and then sexually, are exposed again to low temperatures they will reproduce asexually once more and at the same time reduce their gonads. In the females, therefore, the processes of production of buds and of germ cells respectively are reversible ones affecting the same type of cell material, i. e. the undeterminated ectoderm cells of the manubrium. From the experiments it appears that the males do not have the same ability. It seems to be true therefore, that all ectoderm cells in the males are determinated definitely and irreversibly after the change from asexual to sexual reproduction. 19. The experiment of rearing primary medusae in constant low temperature conditions did not give a clear result; some of the medusae produced only buds for a long time. Other medusae, especially those which had reached a greater age, started producing germ cells. It should therefore be taken into account, that in old medusae internal factors may influence or negative the effect of temperature. 20. With reference to the last mentioned experiment, the younger secondary medusae are in any case able to transfer the tendency of budding to succeeding generations. In lower temperature conditions, therefore, budding will not be wholly suppressed as will happen in the youngest generation of secondary medusae reproducing only sexually if the temperature rises above the higher critical level. 21. So by examination of the seasonal occurrence of the medusae, its reproductive behaviour, the local temperature conditions and the experimental investigations it has been proved that Rathkea is adapted to the temperature of its habitats and represents a „propagative stenotherm“ species (Ekman, 1935). The final conclusion is that the seasonal occurrence and geographical distribution of this species depend entirely on the conditions of temperature.

Description / Table of Contents: Summary Claude Bernard ascribed to the counter-proof a fundamental role in his experimental method and the reasoning on which the method rests. He saw the only proof of the causal nature of a given phenomenon in the fact that the effect fails to appear after elimination of the alleged cause. However, the experimental counter-proof still remains an experiment; the logical structure of both proof and counter-proof, is the same; it is true that the proof calls for a counter-proof; but the latter in its turn calls for the proof as for its counter-proof. One thus arives at an infinite chain of experiments, each link referring to each other as to its proof or counter-proof. This experimental work, nevertheless, comes to its end, though at a moment still chosen more or less arbitrarily; the work continues however in the thought of the experimenter, thus passing from individual results to generalization. There is embodied in the experimental method and in experimental thought a reasoning by analogy. The “sense of determinism” (“sentiment du déterminisme”:Claude Bernard) and the causal thought on which this sense rests rather than the number of proofs and counter-proofs emerge as the ultimate criteria of experimental truth.

Description / Table of Contents: Résumé Dans cette étude nous avons l'intention de proposer une définition de fonction en biologie. D'abord nous avons délimité le problème et faisons remarquer qu'une définition ne doit pas être mise en rapport avec des hypothèses comme la relation causale entre forme et fonction, phylogénèses ou évolution, mais que seule l'existence de fonctions doît être considerée. Les éléments qui doivent être exprimés sont: la relation de fonction à la forme, le caractère dynamique, l'intégration dans l'activité de l'organisme total, la possibilité de fonctions latentes et le fait qu'au cas de fonctions méchaniques le fonction même n'est pas action, mais y est immédiatement relative. Ainsi nous proposons la définition suivante: Une fonction biologique est une propriété d'une partie définie de l'organisme total, marquée par une certaine forme ou structure, laquelle propriété est activité actuelle ou potentielle elle-même, ou bien directement relative à l'activité et par laquelle le développement et le maintien de l'organisme total est mis à même d'avancer harmonieusement. Nous avons fini en faisant quelques remarques théoriques, où nous avons exposé que la fonction dépend logiquement de la forme. C'est pourquoi forme et fonction ne sont pas un exemple du principe de complémentement comme cela a été prétendu parMeyer-Abich. Nous avons également fait attention à une étude antérieure deBarge touchant le problème forme-fonction. Cette étude a servi comme point de départ à la discussion présente.

Description / Table of Contents: Zusammenfassung DieHaeckel'sche Rekapitulationstheorie wird durch die folgende Rekapitulationsregel erweitert: Bei der ontogenetischen Rekapitulation der erscheinungsbildlichen Leistungen ist die Rekapitulation der phylogenetischen Auslesefaktoren der entsprechenden erbildlichen Fähigkeiten Manifestationsbedingung. Der phylogenetische Auslesefaktor bewirkt als ontogenetischer Manifestationsreiz die Genaktivierung. Auslesefaktor ist derjenige Faktor der äusseren oder inneren Umwelt, an den in der Phylogenese die Anpassung erfolgt ist. Im Bereich der inneren Umwelt ist daher die erscheinungsbildliche Leistung der vorhergehenden Entwicklungsstufe sowohl der phylogenetische Auslesefaktor für die erbbildliche Fähigkeit der nachfolgenden Entwicklungsstufe als auch der ontogenetische Manifestationsreiz für die erscheinungsbildliche Leistung der nachfolgenden Entwicklungsstufe. Die erscheinungsbildlichen Leistungen können als reizabhängige Modifikation auftreten, die also vom Manifestationsreiz abhängig bleibt und nach seinem Aufhören auch wieder verschwindet, sie können aber auch als reizunabhängige Dauermodifikation auftreten, die also vom Manifestationsreiz unabhängig wird und nach seinem Aufhören erhalten bleibt, weil das durch den Reiz einmal aktivierte Gen sich im Status des Aktiviertseins bei der Zellvermehrung von Zelle zu Zelle und bei der Vermehrung der Organismen von Generation zu Generation fortpflanzt. Damit ergeben sich neue Möglichkeiten einer Deutung der Kausalzusammenhänge bei der phylogenetischen Evolution und Involution, sowie neue Ansätze einer Erklärung des Evolutionsmechanismus der Reifung und des Involutionsmechanismus des Alterns in der Ontogenese, sowie der dabei auftretenden Erscheinungen der Acceleration und der Retardation.