“ The head of any agency (other than any agency represented under section 1 (b) hereof) to which the President from time to time assigns responsibilities for the implementation of national security policies, shall assign a representative to serve on the Board when the Board is dealing with subjects bearing directly upon the responsibilities of such head. Each such representative shall be an Under Secretary or corresponding official and when so serving such representative shall have the same status on the Board as the members provided for in the said section 1 (b) . ”

“ Each head of agency referred to in items (1) to (4) , inclusive, in this section 1 (b) may provide for an alternate member who shall serve as a member of the Board in lieu of the regular member representing the agency concerned when such regular member is for reasons beyond his control unable to attend any meeting of the Board ”