The 1a, 1b and II fibers terminate on cells in Clarke's nucleus . There are three of these peduncles. It's a crying shame that Clarke's nucleus is not present at every spinal cord level. However, think about a 1a, 1b or II fiber coming in at spinal level L5. It looks around and there is no Clarke's nucleus to hitch a ride on.
Some instructors are fearless enough to talk about a ventral spinocerebellar tract.