In Lord of the Flies, how does Jack appear on the beach and who takes responsibility for the events on the island at the end of the novel?

At the end of the novel, naval officers arrive to rescue
the boys and return them to civilization.  Upon their arrival, the naval officers ask
who is in charge on the island.  Jack, who struggled against Ralph for power for the
entire novel (and who was described as a hunter, a leader, and a savage), begins to take
responsibility, but stops:

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A little boy who wore the remains of an
extraordinary black cap on his red hair and who carried the remains of a pair of
spectacles at his waist, started forward, then changed his mind and stood
still.

It's important to note
that with this description of Jack, Golding essentially renders Jack powerless.  He is
no longer a fearless leader; he is no longer a hunter who wants, in the worst way
possible, to be in charge.

Instead, Ralph, the "fair" boy
who longs for order, states that he is in charge.  It is Ralph who understands the
gravity of the situation in which he and the others have found themselves, and further,
he understands the innocence he has lost in the process of surviving on the
island:

Ralph
wept for the end of innocence, the darkness of man's heart, and the fall through the air
of the true, wise friend called
Piggy.