Of the metre-wavelength solar radio bursts which have been recognized, those of type II are characterized by the most complex set of spectral features. Apparently acceptable explanations have now been put forward for most of these features. However, not all these explanations can be considered to be established. In particular the phenomenon of band splitting has been explained in different ways by Sturrock, by Tidman et al., by Zheleznyakov and Zaitsev. However, the theories of Sturrock and Tidman apparently require magnetic fields so strong as to preclude the formation of a magnetohydrodynamic shock wave by a disturbance moving at the velocity (< 1000 km/s) attributed to type II bursts. The same problem is encountered in other earlier theories of band splitting involving magnetic effects. The other theory does not involve the magnetic field strength. However, the details of this theory do not appear to have been properly worked out as yet.