Riddle 104

My first is often broken, ’t is so frail;
Sometimes it has a head, sometimes a tail;
Lives in the water, worn upon the hand,
Dooms the offender, represents a land.
My last is found on mankind and on brute,
Possessed alike by fish and fowl and fruit.
The daring mariner who seeks the pole,
Failing to find it, may secure my whole.