The spectrum of magnons localized in an isolated 180-degrees domain wa
ll in a YIG single crystal has been studied as a function of the densi
ty of Bloch lines and their structure. An induction method and a magne
tooptic method were used. A dynamic transformation of the structure of
Bloch lines has been observed to result from drift, generation, and a
nnihilation of Bloch points, which cause substantial changes in the ch
aracteristics of bending vibrations of the wall.