Curve Degree
Changes the degree of the picked blend curve(s).
Five tools are available on the Curve Degree pull-out: choose from degree 1, 2, 3, 5, or 7.
Access these tools from the Blend Curve Toolbox:
Pick the blend curve or curves you want to edit, then choose the tool corresponding to the degree you want for the underlying curve.
Note: When you change the degree of a blend curve, surfaces constructed from the blend curve are also rebuilt to the new degree (unless they have constraints of their own that prevent regeneration).