When a system is founded upon class, how can caste be prevented?
The Iron Heel will not be able to prevent it, and in the end caste will destroy the Iron Heel.

The oligarchs have already developed caste among themselves; but wait until the favored unions develop caste.

The Iron Heel will use all its power to prevent it, but it will fail.
"In the favored unions are the flower of the American workingmen.

They are strong, efficient men.

They have become members of those unions through competition for place.