The mathematical description of the spherulitic pattern formation during nonisothermal crystallization in infinite samples was elaborated on the basis of the assumption of the momentary randomness of primary nucleation. The dependence of the conversion degree of a melt into spherulites was also obtained. The probabilities of the formation of the spherulitic inner points and boundaries were evaluated for the time dependent primary nucleation rate and spherulite growth rate. The time distributions of the formation of the spherulite interiors and boundaries were derived. The area (or length) of the boundaries as well as the number of multiple boundary points dependent on the time of their formation was also determined.