325 who, by June 30 of the calendar year in which appointed, will have completed at least three years of service in the Regular Marine Corps in the grade of warrant officer, W - 1, or above. To be eligible for appointment under this subsection to the grade of lieutenant, lieutenant (junior grade), or ensign on the active list of the Navy or captain, first lieutenant, or second lieutenant on the active list of the Marine Corps, members must be under 40, 35, and 32 years of age, respectively, on June 29 of the calendar year in which they are to be appointed. (b) Original appointments to the active list of the Navy in the line and in any appropriate staff corps in the grade of ensign may be made from male enlisted members of the Regular Navy. To be eligible for such an appointment a member must be under 33 years of age on the date of appointment and must have had at least four years of continuous service, immediately preceding the date of his appointment, in the Regular Navy. (c) Before he may be appointed under this section, a member must apply for appointment, must be recommended by a commanding officer under whom he has served in the grade he holds at the time he applies, and, under regulations prescribed by the Secretary of the Navy, must establish his qualifications by— (1) recommendation of a naval examininfi: board that he is mentally, morally, and professionally qualified; and (2) findinn; of a board of medical examiners that he is physically qualified. A member who twice fails to establish his qualifications is ineligible for appointment under this section. (d) Each appointment under subsection (a) shall be in the grade for which the member applies and for which he is found qualified. (e) Each officer appointed under this section in the grade of lieutenant in the line of the Navy or in the grade of captain in the Marine Corps is an additional number in that grade only and, while in that grade, becomes eligible for consideration for promotion when the officer next senior to him becomes eligible. (f) An officer appointed under this section may not suffer any reduction in the pay and allowances to which he was entitled at the time of his appointment because of his former status. § 5587. Regular Navy: officers designated for engineering duty, aeronautical engineering duty, and special duty (a) Male persons may be originally appointed to the active list in the line of the Navy as officers designated for engineering duty^ aeronautical engineering duty, or special duty. Each person so appointed shall be appointed in the grade of— (1) ensign, if designated for engineering duty, aeronautical engineering duty, or any type of special duty for which a graduate degree is not required: or (2) lieutenant (junior grade), if designated for a type of special duty for which a graduate degree is required. The number of appointments in each of these grades and designations may not exceed, in any fiscal year, the number of vacancies that the Secretary of the Navy estimates will occur in the fiscal year for officers of the grade and designation concerned.