The influence of varied relaxing and fixing conditions on anatomical characters in a Planorbis species

Dimensions and length ratios of reproductive organs in Planorbis intermixtus Mousson were compared in snails fixed after complete and incomplete relaxation with pentobarbital or nembutal and in snails killed in alcohol without relaxation. The only organ significantly changing its length is the preputium. Its dimensions should be used in taxonomy only when the fixing conditions are the same. Any other parts of the reproductive system including the penis sheath in this group do not differ significantly between animals killed with or without relaxation.