Distributions of giant H II regions and OB associations are used to determine the reproductivity, y, for O stars in M33 and the percentage of O stars formed by a spiral density wave. Star formation in M33 is compared to star formation in the earth Galaxy; both galaxies are characterized by an empirical linear relation between y and tau(seq), the time interval between sequential generations. For both galaxies, the larger the values of tau(seq), the smaller the value of y and the smaller percentage of O stars formed by sequential star formation. The results indicate that in the central disk of M33 at an extreme tau(seq) value = 3,000,000 years, y = 0.94 and only 6% of the O stars are formed by a density wave; if the typical value of tau(seq) is 35,000,000 years, then y = 0.51 and 49% of the O stars are formed by the spiral density wave. It is concluded that y is a factor of 1.1-3.1 larger in M33 than in the earth Galaxy. The percentage of O stars owing their origin to a spiral density wave is a factor of 1.4-11.7 larger in the earth Galaxy than in M33. The larger values of y in M33 are a result of the higher surface densities of gas and the smaller drift speeds in M33.