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1. The relationship between water temperature (T°C) and brood development time (d days for embryonic development time plus •post-hatch time') was investigated experimentally using animals from four populations of Gammarus fossarum (populations 1-4) and two populations of C. roeseli (populations 5 and 6) in Austrian streams.2. Eleven mathematica] models were examined as suitable functions to describe the relationship between d and T. The models were compared with respect to their goodness-of-fit and suitability for further quantitative, statistical analyses of intra-and interspecific differences between natural populations of G. fossarum and G. roeseli.3. Statistical analyses were performed with logarithmically transformed values of d. in order to provide homogeneous variances between the different constant temperatures used. The following three-parameler model was found to be the most suitable for the data: d=a exp [-^1 In T~CiT\.

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Two models are studied to describe the spread of foot-and-mouth disease during the 1973 epidemic in Austria. The models are modifications of a three-class-model (due to KEEMACK and MCKENDRICK) taking into account the special character of the disease 88 well a8 control methods (stamping-out-method, vaccination programs).