From the analysis of the behaviour it is evidenced that the biological peculiarities of the Hypotrichs depend on the close linking between the adaptive strategies they have found to environmental problems. The loss of the envelope surface of the other ciliates was followed, in the Ciliates evolution, by the acquisition of the "cirrus and membranelle" propulsive logic. Furthermore they acquire a strong-and-easy-to-release adhesion system to creep on the substrate. The eco-ethological approach showed that they are capable of adapting to an environment characterised by new dimensional scales, new micro-environments and also new stimuli.