The author continues his treatment of the relation between the birth and population functions pertaining to [female][female]. He shows that when one is a polynomial in t, the time, the other is also a polynomial in t; and that when one is of the form of a logistic curve, so is the other. The author develops a formula for the birth function as a series in terms of the population functions and its derivatives. Very good results are obtained for certain periods when the birth function is a linear function of the population function. The formulas are applied to data from different countries.