Q: icloud calendar won't sync to iCal on iphone, but will sync to other calendar program on iphone

I am using Mountain Lion on my Macbook Pro.  All my calendars are in iCloud.  But no more than one of a dozen calendars syncs to the iPhone.

I have another calendar program - WeekCal - on the phone and that syncs fine.  I can watch it happen.  But iCal...no.