成唯識論演祕 4.266

4.266

異熟六識雖不能熏，同於第八。然現望種無能持力，不同八現與種為依，故不取也。

Although the six maturation-consciousnesses cannot perfume and are in that respect like the eighth, their active manifestations lack the power to sustain seeds and are not like the eighth's active manifestation acting as a basis for seeds; therefore they are not included.