Among the numerous classes of risks now undertaken by Insurance Companies, those against the contingency of leaving issue are beginning, from their increasing numbers, to assume a position of greater importance than heretofore. Nothing has hitherto, to my knowledge, been written upon the subject, and the premiums for insurances of this nature have been left to the judgment of the actuary as each individual case has come before him, there being no recognized and accurate formula for the calculation of the risk. Under these circumstances, and as a considerable amount of material exists from which approximate results may be deduced, I venture to submit to the Institute a few considerations upon the subject, but confined principally to the probabilities of marriage so far as they affect the calculation of such premiums.