Section 29. Sections nineteen, nineteen A and twenty-two to twenty-eight, inclusive, shall not apply to those zoos approved by the United States department of agriculture. Natural history associations and museums, or zoos not approved by the United States department of agriculture which are operated by the commonwealth or any political subdivision thereof may, at the discretion of the director, be exempt from the provisions of said sections. Sections twenty-four to twenty-eight, inclusive, shall not apply to persons holding authorization from the director under clause (2) of section four.

Nothing contained in this section shall be construed so as to permit such zoos, natural history associations or museums to transfer any fish, fish spawn, birds, the nest or eggs thereof or mammals protected by this chapter to any person by means of sale, exchange, barter, gift, donation or otherwise unless so authorized in writing by the director.