Die Torsion der Gastropoda - ein biomechanischer Prozeß

The recently proposed biomechanical model of gastropod torsion (edlinger 1988 a, b) is rejected on various reasons. First, the assumed original conditions in Polyplacophora and Tryblidiida as well as the constructed original condition in the Gastropoda do not emst in reality. Secondly, the mollus-can musculature is a very dynamic structure (continuous assembly and disassembl) so that biomechanic rocesses are of much minor importance than assumed by Edlinger . Thirdly, the biomechanical model resented does not explain the change of the relative position of the lateral (= visceral) nerve cords which are surrounding the dorsoventral muscles in Polyplacophora and Tryblidiida (also Scaphopoda and Bivalvia), but are situated between the muscles in Cephalooda and Gastropoda. The consequences of these considerations to the early evolution of Gastropoda are briefly outlined.