It is well-known that hyponormal operators have many interesting properties, for example, if the restriction T | M of the hyponormal operator T on its nontrivial closed invariant subspace M is normal, then M reduces T . In order to discuss the reducibility of invariant subspaces of an operator, four properties of invariant subspaces (R i , i = 1, . . . , 4) are introduced. Among others, it is proved that, for a k-quasi-A(n) operator T , if the restriction T | M is normal and injective, then M reduces T , thus the function σ : T −→ σ (T ) is continuous on the class of k-quasiclass-A(n) operators. Some examples related to class A(n) and n-paranormal operator are given which imply that the inclusion relations are strict.