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The possibility of electrosensitivity of the Desman in immersion is tested by the method of conditioning : neither spontaneous nor obvious responses linked to the stimuli (overt responses) was noticed. The unique animal kept in captivity was tested in the experimental tank. Single or repetitive (sine or square) stimuli were applied through 2 silver wire electrodes. Intensities, possible in a natural environment, in the range of lO mV/cm, remained without response. Stimuli of much higher magnitude (3 - 10V between the electrodes) which can be considered as giving a « mild » electroshock provoked a slight retraction of the trunk. These shocks were felt, on the tongue of the experimenter, as galvanic electricity. The Desman therefore showed a sensibility close to that of man. From these results we can suggest, as an hypothesis, that the electrical sense is rather improbable with Mammals « sensu stricto ». This is the case of the Desman which can be considered as an animal well adapted to subaquatic life, although not living under selective pressure in its narrow ecological « niche »: it does not show any significative response to electrical activities of biological origin (electromyograms). It distinguishes itself from the Platypus (Monotremata, Prototheria), which lives in a similar environment and shares the same diet as the Desman : it possesses an evident electrosensitivity. Formerly adapted to a new habitat it has apparently developed an electrical sense secondarily, which lower aquatic Vertebrates have originally always possessed and used for orientation in electrical field to detect and catch preys

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