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Notes: Summary It is known that numerous gastropods show homing ability. Many limpets return to well defined sites. Patella L. acquires a home spot also on the smooth glass surfaces of aquarium. Before leaving, the limpet scrapes its home, particularly the anterior part of the footprint. After each return it makes characteristic movements with its shell. When homing Patella nearly always retraces its outward track, at least in part; sometimes it reaches its home over the shortest route possible. Site and tracks are marked by chemical substances. The animal orientates itself by contact chemoreception on the track and by distance chemoreception when near its home. Apparently there also exists a kinesthetic mechanism of orientation based on a measurement of distance on the outward journey. At the home spot Patella always manoeuveres exactly into the same position. Often it has to turn or to glide around slightly. It finally settles down with small movements of its shell. The footprint shows chemical differences in a wide marginal zone. Probably, different chemoreceptors on the sole of the foot are associated to the various regions of the footprint. The chemical differentiation of the footprint has the same orientation-value for all individuals of the same size group. In addition there exists an individual marking, shown e.g. by avoidance reactions of alien animals. The individual specificity of the foot's secretum is particularly marked on the tracks, for each Patella follows its own trail only and thus normally reaches its own home. On an uneven substratum this is the only place where the margin of its shell fits the ground exactly. For establishing a home site and keeping to it, several environmental conditions have to be met. Patella settles only on surfaces overgrown with small algae. In an aquarium it favours the sides most exposed to light. On vertical walls the animal is gravity-oriented. Most limpets are attached head-end down. Patella is able to perceive the distance from the water-line, and may orient itself with respect to fixed objects in the aquarium by means of a “Ferntastsinn”. When first choosing a home spot on an uneven substratum, the limpet often adjusts its position by turning movements, so that the contacts between shell and ground are as close as possible. Selective growth at the shell's margin then results in a perfect fit to the irregularities of the ground. All prerequisites for the establishment of a home site are also determining the animal's keeping to its home. If changes are introduced with respect to the fitting of the shell to the ground, to the position of neighbouring objects, to water-level, light, or direction of gravity, the animal may leave its home site and reorient itself in an equivalent new one. The attractiveness of the chemical markings of the old site nevertheless compete with all these conditions for some time. Rest and activity are controlled by light-dark and tidal cycles. — Inter-and intraspecific differences were obtained under experimental conditions. Almost all individuals were preferentially active in darkness. P. caerulea moved at high tide; P. vulgata was active either at low tide only, or both at high and low tide, or — rarely—at high tide only. All animals reacting to tidal rhythms were synchronized even by unnaturally frequent changes in the water-level. The tidal dependence of the activity of individual P. vulgata may perhaps be interpreted as the persistence of an adaptation to drought and submergence acquired at the original habitat. The reactive ability towards high and low tide can be modified. The activity-phase may be stopped prematurely by changing light or tidal conditions. Animals keeping constantly to their homes returned to them at once, whereas others — having no defined home —generally prolonged their excursions. When light and water-level are kept constant the locomotory activity of P. vulgata and P. caerulea has the characteristics of an endogenous tidal rhythm. Changes in water-level soon approximately catch the freerunning periodicity, alteration of light and darkness synchronize it less readily but more precisely.

Notes: Zusammenfassung der Ergebnisse 1. Der Kokon von Cemiostoma susinella L. besteht aus 3 Schichten (dem H-förmigen Dachgespinst, dem breitellipsioden Außenkokon, dem gerstenkornförmigen Innenkokon), die durch 2 senkrecht aufeinander stehende Symmetrieebenen in 4 deckungsgleiche Teilstücke zerlegt werden können. Die Raupe führt entsprechend den 4 Teilstücken in 4 verschiedenen Stellungen die gleichen, für jede Spinnphase charakteristischen (ausführlich beschriebenen) Spinnbewegungen aus. Kein Teilstück wird in einem Arbeitsgang sondern stets erst nach häufigen Stellungswechseln, die in streng gesetzmäßiger Weise aufeinander folgen, vollendet. 2. Der Kokonbauinstinkt von C. susinella ist nach Beendigung der Spinntätigkeit abgeklungen und nicht erneut auslösbar. Die Raupe „kann” aber, aus einem nicht fertiggestellten Kokon herausgenommen, ein neues 2. Puppengespinst (geringere Fadendichte!) mit allen seinen Einzelteilen bauen. 3. Die verpuppungsreife Larve meidet direktes Sonnenlicht and „sucht” schattige (Blattunterseite) bzw. dunkle (Experiment) Stellen auf. Die Bodenfläche (Blattunterseite oder im Experiment die Glaswand) muß in einem bestimmten Grade in einer Ebene gekrümmt sein. Ebene Flächen werden nicht besponnen, kugelige Fläehen werden gemieden. Zwischen dem Krümmungsradius der Bodenfläche und der Länge des Dachgespinstes bestehen feste Beziehungen. Bei sehr kleinen Krümmungsradien orientiert sick die Larve schräg zur Krümmungsebene. Mit Hilfe einer „Krnmmungsorgel” wurde das „Krümmungsoptimum” der C. susinella-Larve bestimmt.

Notes: By polymerisation of ethylene dimethacrylate with n-butyllithium in solution reactive microgels have been obtained. These EDMA-microgels are nearly spherical, have a broad distribution and are easily swellable in organic solvents. The macrogelation depends on the amount of solvent between the microgel particles.

Notes: The thermal polymerization of styrene in emulsion was studied by determination of the number of particles, the rate of polymerization, and the average molecular weight of the polymer formed as a function of the emulsifier concentration. For the number of particles the relation N ∼ [E]1,4 was found, whereas the rate of polymerization showed a dependence of vbr ∼ [E]0,7, only up to an emulsifier content of 0,2 mol. dm-3, but remained constant at higher concentrations. A transfer of low molecular weight radical species from the organic to the aqueous phase is discussed as a prerequisite of polymerization in the latex particles. The deviations from the Smith-Ewart theory are explained by the low rate of radical formation, which does not provide a constant radical concentration per particle.

Notes: The self-emulsifying copolymerization of unsaturated polyesters (UP) with various acrylic and methacrylic esters was studied. The structure of comonomers significantly influences the character of microgels obtained. Among these monomers the copolymerization of UP with methyl methacrylate (MMA) was investigated in detail in order to make clear the behavior of this polymerization as compared with that of styrene. The water/monomer and UP/MMA ratios were found to be the most important factors controlling the molecular weight and solution viscosity of the microgels. The relationship between M̄w and intrinsic viscosity of microgels suggests that the microgels from MMA have less compact structure than those from styrene.

Notes: Reactive microgels containing sulfo groups were prepared by copolymerization of N,N′-methylenediacrylamide (1) and 2-acrylamido-2-methylpropanesulfonic acid (2) in water. The composition of the microgels, their structure, density, molecular weight and viscosity in solution were examined depending on the composition of the monomer mixture and the reaction conditions.