In all these cases the torsion and asymmetry of the body are unaffected.
There is nothing in their mode of life which will afford an explanation of the asymmetry which is a developmental phenomenon.
Lanceolatus obtained by the tow-net in 8 -10 fathoms, showing the asymmetry of the large lateral sinistral mouth with its ciliated margin cm and the dextral series of simple primary gill-slits (Ips-14ps).
As an example of extreme asymmetry we may take de Vries's record of the frequency with which given numbers of petals occur in a certain race of buttercups.
When the shell is sinistral the asymmetry of the organs is usually reversed, and there is a complete situs inversus viscerum, the direction of the spiral of the shell corresponding to the position of the organs of the body.