Act III, Scene 1, whom does Antony refer to when he says, " The choice and master spirits of this age"?Julius Caesar by William Shakespeare

After Brutus and the other conspirators have slain Julius
Caesar, Brutus instructs them to wipe their hands and their swords in Caesar's blood
prior to their going out into the streets of Rome to speak to the people.  However,
before they reach the streets to explain to the Romans what has happened, a servant of
Marc Antony approaches them with flattery before reciting his master's request to speak
with all of them. When Brutus agrees, Cassius, however, considers killing
Antony.

In the first scene of Act III of Julius
Caesar as Antony arrives, he speaks first to Caesar, addressing him as
"shrunk to this little measure" and bids him farewell.  Then, he tells Brutus and the
other assassins that he does not know what they intend to do, and whom else they
consider corrupt, but he is ready to die as it is a good hour since their swords are
covered with Caesar's noble blood.  For, Antony says, there is no better place to die
than by Caesar.  Antony tells the conspirators that he cannot imagine a better death
than being stabbed by them, and with hyperbole, he calls them "The choice and master
spirits of this age," the masters of their
era. 

It is, of course with irony that Marc
Antony tells Brutus and the conspirators that they are in control of Rome and what has
occurred.  For, if he attains permission to give a funeral oration for his noble friend,
Caesar, Antony intends to foment the crowd and stir them to rebellion.  Dissembling,
Antony shakes each one's bloody hand when Brutus gives him
permission.