Asymmetry Revisited

Interest in the developmental basis of symmetry and asymmetry,as old as experimental embryology itself, has recently becomereactivated. A brief survey is made of recent or current activitiesin the following areas: (i) development of asymmetry in thechick limb bud, as related to the so-called zone of polarizingactivity (Saunders et al.); (ii) situs inversus viscerum inamphibians, as induced by transplantation and defect experiments,radiation, and chemical treatment (von Woellwarth, von Kraft,Wehrmaker); (iii) situs inversus viscerum in mammals as relatedto (a) twinning (Cockayne, Torgerson, Baker-Cohen); (b) genetics(Feldman, Cockayne, Torgerson for man, Tihen et al., Hummeland Chapman for mouse); and (c) teratogens (Layton and associates);(iv) ultrastructure in snails (Morrill and Perkins); (v) asymmetrydeveloping as a result of changes in chemical instability inhomogeneous systems (Ortoleva and Ross); (vi) asymmetrical mentality(Sperry and associates). No general conclusions are attempted.