[I.55] Antonius Pope | Antonio Ff (and so elsewhere).
[I.56] It was an old custom at these festivals for the priests, naked except for a girdle about the loins, to run through the streets of the city, waving in the hand a thong of goat's hide, and striking with it such women as offered themselves for the blow, in the belief that this would prevent or avert "the sterile curse." Cæsar was at this time childless; his only daughter, Julia, married to Pompey the Great, having died some years before, upon the birth of her first child, who also died soon after.
[I.57] [Flourish] Ff omit.
[I.58] the Ides of March: March 15th.
[I.59] soothsayer. By derivation, 'truth teller.'
[I.60] Coleridge has a remark on this line, which, whether true to the subject or not, is very characteristic of the writer: "If my ear does not deceive me, the metre of this line was meant to express that sort of mild philosophic contempt, characterizing Brutus even in his first casual speech."
[I.61] Sennet. This is an expression occurring repeatedly in old stage directions. It is of uncertain origin (but cf. 'signature' in musical notation) and denotes a peculiar succession of notes on a trumpet, used, as here, to signal the march of a procession.
[I.62] Scene III Pope.
[I.63] gamesome: fond of games. Here as in Cymbeline, I, vi, 60, the word seems to be used in a literal and restricted sense.
[I.64] quick spirit: lively humor. The primary meaning of 'quick' is 'alive,' as in the phrase "the quick and the dead." See Skeat.