Some mechanisms of adaptation to the wet microhabitats in higher geophila (Mollusca, Pulmonata)

Most snails dwelling in wet microhabitats (lower layers of fallen leaves; w et screes etc.) are relatively small. They have problems of locomotion beca use of the complexity of their habitats and particularly because of water g ripping the shell through surface tension. I recognize four adaptations to these conditions: 1) water repellent conchioline hairs on the shell surface (some Helicoidea, Polygyridae); 2) apertural teeth that facilitate control of the shell's position (some Helicoidea and Endodontinae); 3) fusion of t hree branches of the columellar muscle into one, so that it is hard enough to drag the shells through the obstacles (Zonitinia, Oreohelix); 4) shell l oss;leading to appearance of the slugs. The second and the fourth mechanism s evolve probably through a positive feedback mechanism operating between m orphology and environment.