Any member of the fire department who completes at least 25 years of service in the aggregate and attains the age of 50 years, said service to be computed under Section 8.578, may retire for service at his option. Members shall be retired on the first day of the month next following the attainment by them of the age of 65 years. A member retired after meeting the service and age requirements in the two sentences next preceding, shall receive a retirement allowance equal to 55 percent of the final compensation of said member, as defined in Section 8.569, plus an allowance at the rate of three percent of said final compensation, for each year of service rendered in excess of 25 years; provided, however, that such retirement allowance shall not exceed 70 percent of said member's final compensation. A member retired after attaining the age of 65 years, but before completing 25 years of service in the aggregate computed under Section 8.578, shall receive a retirement allowance which bears the same ratio to 50 percent of the final compensation of said member, as defined in Section 8.569, as the service with which he is entitled to be credited, bears to 25 years. If, at the date of retirement for service, or retirement for disability resulting from an injury received in performance of duty, said member has no wife, children or dependent parents, who would qualify for the continuance of the allowance after death of said member, or with respect to the portion of the allowance which would not be continued regardless of dependents, or upon retirement for disability resulting from other causes, with respect to all of the allowance and regardless of dependents at retirement, a member retired under this section, or Section 8.571, may elect before the first payment of the retirement allowance is made, to receive the actuarial equivalent of his allowance or the portion which would not be continued regardless of dependents, as the case may be, partly in a lesser allowance to be received by him throughout his life, and partly in other benefits payable after his death to another person or persons, provided that such election shall be subject to all the conditions prescribed by the Board of Supervisors to govern similar election by other members of the Retirement System, including the character and amount of such other benefits.