The flexible body structure of polystomes (Monogenea: Polystomatidae) encumbers taxonomic classification and species identification. Large intraspecific and limited interspecific variation in the morphology of polystomes further complicates the identification of species. Apart from employing the host-specific nature of the polystomes, taxonomic characterisation relies heavily on the sclerotised skeletal structures, such as the hamuli and the marginal hooklets. The currently accepted measurement system for marginal hooklets appears to be non-optimal and an improved protocol is needed. This paper describes in detail how such a protocol is found by evaluating various sets of measurements statistically in order to identify the most informative combination of parameters. Thirteen measurements of marginal hooklets from 11 different Southern African Polystoma species were taken and evaluated. A new protocol for discriminating between species of Polystoma Zeder, 1800, that employs only three measurements, is proposed. The value of the processes to derive morphometric protocols, as described, is that it is not restricted to a specific taxon, but that it can be amended and applied to any taxonomic grouping.

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We report the results of an experiment on the rolling motion of a loaded hoop. The data are obtained using a high-speed video camera, and the motion is analyzed on a frame-by-frame basis. Our analysis demonstrates that the experimental results are in reasonably close agreement with previously reported theoretical results.

The logistic map, whose iterations lead to period doubling and chaos as the control parameter, is increased and has three cases of the control parameter where exact solutions are known. In this paper, we show that general solutions also exist for other values of the control parameter. These solutions employ a special function, not expressible in terms of known analytical functions. A method of calculating this function numerically is proposed, and some graphs of this function are given, and its properties are discussed.