A Supplement to the act of June 12, 1931 (P. L. 575, No. 200), entitled "An act providing for joint action by Pennsylvania and New Jersey in the development of ports on the lower Delaware River, and the improvement of the facilities for transportation across the river; authorizing the Governor, for these purposes, to enter into an agreement with New Jersey; *** and making an appropriation," prohibiting commissioners, officers and employes from engaging in certain activities.