Each company which shall have made the deposit provided for by the act mentioned in section 246, shall make additional deposits from time to time in amounts of not less than five thousand dollars of securities which are authorized investments for life insurance companies under this Code, so that the market value of the securities deposited shall always be equal to the reserve value of the policies heretofore registered by said company, less such liens (not exceeding such net value) as the company may have against them.