Subcutaneous injections at varying intervals, of a saline emulsion of 200 eggs laid by an infective lot of mosquitoes produced no reaction in 6 normal M. rhesus monkeys. Negative results were also obtained in 5 biting and 2 injection experiments with progeny of the same infective lot of mosquitoes in which 7 normal monkeys were used. The eggs consisted of batches laid after the 1st, 2nd and 4th blood-meals of the original lot; the last feeding occurred 41 days after the initial infecting meal. The imaginal offspring represented rearings following the 1st, 2nd and 5th blood-meals of the parent lot. The last feeding occurred 54 days after the 1st. It is concluded that under the conditions of the experiments here reported hereditary transmission of yellow fever by A. aegypti is improbable Variations in age and in number of blood-meals of parent and offspring mosquitoes had no effect in achieving passage of the virus from one stage of the insect to another.