注大乘入楞伽經 8.203

8.203

此明五識不覺諸法自心現故，取種種塵，隨取即滅，故言次第滅。隨次第滅時，即六識生，故言別識生起。意識與彼五識共俱，取於五識所取種種差別形相，一念時不住，是名剎那也。

This clarifies that because the five consciousnesses do not awaken to phenomena being manifestations of one's own mind, they grasp various sense objects and immediately cease upon grasping them; therefore it is said: 'they cease in succession'. When they cease in succession, the sixth consciousness arises; therefore it is said: 'another consciousness arises'. The mental consciousness operates together with those five consciousnesses, grasping the various differentiated forms grasped by the five consciousnesses, without abiding for even a single thought-moment; this is called momentary.