The term "employment" shall not include service performed by an insurance agent, insurance broker, or insurance solicitor or a real estate broker or a real estate salesperson to the extent he or she is compensated by commission and service performed by an investment company agent or solicitor to the extent he or she is compensated by commission. The term "investment company", as used in this section is to be construed as meaning an investment company as defined in the act of congress entitled "Investment Company Act of 1940."