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Statistical examination of the data from experiments conducted on groups of Amphibians induces us to retain as plausible the hypothesis which indicates in fasting one of the preminent factors that cause an increase in the melanic content of their liver. The temperature does not act directly, but indirectly, on the process of melanosynthesis, by inducing or otherwise the semilethargous state on which alimentation depends.

Using the Biotic Index and the Diversity Index the results are analysed of a study of the macrobenthic community sampled in the course of one year at three stations along he lowest-lying stretch of the River Simeto. The results obtained from applying the two different indices are not in perfect agreement one with the other. Whereas with the Biotic Index one could be led to consider the fluvial environment situation a good one, the Diversity Index shows the environment to be partially compromised by organic substances. On the basis of results of chemico-physico-microbiological analyses as well as data concerning the nutritive habits of the species found, we conclude that the Diversity Index is a more suitable instrument for measuring the biological reality of the Simeto.

Frogs caught in winter and kept at summer temperatures, show an increase in the melanic content of the liver. Frogs caught in summer and kept at winter temperatures do not show variations in hepatic melanins with respect to the summer control specimes. This data does not correspond with the natural course of hepatic melanin fluctuations, therefore the causes of the variations are to be sought in factors other than the temperature, one of which could very probably be represented by alimentation.